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User`s Manual - Kansas State University

1. i public void startUI field setEnabled true setTitle Demo III agent name setDisplay Client started public void setField field setEnabled true public void setDisplay String m display append m n public static void main String args if args length 2 System out printin Usage java ClientAgentGUI lt name gt lt broadcast address gt System exit 1 54 String name args 0 String broadcastAddress args 1 ClientAgentGUI gui new ClientAgentGUI name gui addWindowListener broadcastAddress new WindowAdapter public void windowClosing WindowEvent e System exit 0 i gui startUIl end of main method end of class agent_interface 55 ClientGetKey package ksu cis example KeyDistribution import ksu cis mom import java io import javax net ssl public class ClientGetKey extends SecureUnicastConversation public ClientAgent parent public ClientGetKey SSLSocket s ObjectInputStream i ObjectOutputStream o ClientAgent a Message m super s i O a m parent a public void run int state 0 boolean notDone true try while notDone switch state case 0 Message reply new Message reply setPerformative ack sendMessage reply output notDone false state 1 break input close output close connectio
2. t new Thread new ClientReceiveFile server input output this m gui t start catch ClassNotFoundException cnfex System out printin Class not found exception in this name catch IOException ioex System out printin IOException in this name public void sendRequest String req 34 StringTokenizer token new StringTokenizer req Thread init init new Thread new ClientRequestFile this token nextToken token nextToken gui init start run method for client It put agent to sleep for 1000 millisec see java lang Runnable run aA public void run while alive try Thread sleep 1000 catch InterruptedException iex System out printin Thread Interrupted in this name 35 ClientAgentGUI package ksu cis example FileSharing import java awt import java awt event GUI for Client agent It has a text field to input what file to request and from whom eg 192 150 121 19 readme txt author Chairoj Mekprasertvit itd public class ClientAgentGUI extends Frame private TextField field private TextArea display private ClientAgent agent Constrcutor for agent_interface param name param broadcastAddress public ClientAgentGUI super Please Wait setLayout new BorderLayout field new TextField displa
3. m sender if m performative equals calculate t new Thread new MulticastServer mSocket multicast_queue this m_port 0 m t startQ In the case of multicast the message is directly passed to the receive method The MulticastSocket mSocket is used to send out multicast messages and multicast_queue is a message queue for the conversation to receive multicast message Then the performative of the message is checked to see if it is calculate In this case this is the only one performative that agent can participate The other performatives are ignored If the agent recognizes the performative it creates a new multicast conversation thread MulticastServer and starts the thread Furthermore agent may start a new component class instead of conversation class if component based architecture is used and the component class will be responsible for starting the conversation 4 3 AgentConversation Class This class is an abstract class that all types of conversation inherit from It is a generalization of all conversations in agentMom package It defines the minimum requirements for a conversation to be in agentMom package It also allows user to easily implement a new type of conversation for agentMom package Sub class of this class should override the sendMessage readMessage and nonblockedReadMessage method and provides at least two type of constructors conversation initiator and conversation respondent U
4. 0 secureMulticastPort try super group new InetAddress 1 super group 0 InetAddress getByName 239 192 100 100 catch Throwable e write Invalid Internet Address MessageHandler h new MessageHandler unicastPort this h start MulticastHandler mh new MulticastHandler this multicastPort 0 1 group 0 mh start receiveMessage method When receive a unicast connection from other agent it find the file in itself If the file not found it send multicast message to the group to send the file instead eo public void receiveMessage Socket server ObjectInputStream input ObjectOutputStream output Thread t Message m try m Message input readObject send accept request if m performative equals find file ServerRespondRequest srr new ServerRespondRequest server input output this m t new Thread srr t stert wait until conversation is done while srr getDone 43 try Thread sleep 1000 catch InterruptedException iex write ServerRespondRequest InterruptedException check if this agent has the file then send back this write The file is m content boolean found this findFile String m content if found ServerReturnFile srf new ServerReturnFile this server getInetAddress getHostName String m content t new
5. Certificates must be created for clients and servers that need to communicate securely using SSL Java 1 4 uses certificates created using the Java keytool shipped with J2SE I used the following command to create an RSA certificate for the server D gt keytool genkey v keyalg RSA Enter keystore password xxxxxx What is your first and last name Unknown chairoj mekprasertvit What is the name of your organizational unit Unknown ksu What is the name of your organization Unknown cis What is the name of your City or Locality Unknown manhattan What is the name of your State or Province Unknown ks What is the two letter country code for this unit Unknown us Is CN chairoj mekprasertvit OU ksu O cis L manhattan ST ks C us correct no y Generating 1 024 bit RSA key pair and self signed certificate MD5WithRSA for CN chairoj mekprasertvit OU ksu O cis L manhattan ST ks C us Enter key password for lt mykey gt RETURN if same as keystore password Saving C j2sdk 1 4 2 keystore D gt Then we need to export the self signed certificate CAj2sdk 1 4 2 gt keytool export keystore keystore file certificate Enter keystore password xxxxxx Certificate stored in file lt certificate gt Note that this is a self signed certificate Alternatively we can generate Certificate Signing Request CSR with certreq and send that to a Certificate Authority CA for signing but this is only experiment
6. ClassNotFoundException cnfex write Error class not found in this name catch IOException ex write Error read unicast input in this name public void sendSecuredMulticast String m Thread init init new Thread new SecureMulticastSend this secureMulticastPort 1 group 1 m gui key algorithm init start public void run boolean alive true gui setDisplay Agent Run while alive 53 ClientAgentGUI package ksu cis example KeyDistribution import java awt import java awt event public class ClientAgentGUI extends Frame private TextField field private TextArea display private ClientAgent agent public ClientAgentGUI String name String broadcastAddress super Please Wait setLayout new BorderLayout field new TextField display new TextArea add display Center display setBackground Color white display setForeground Color black add field South setSize 300 200 setVisible true show agent new ClientAgent name broadcastAddress this Thread t new Thread agent t start create field for outgoing secured multicast message field setEnabled false field addActionListener new ActionListener public void actionPerformed ActionEvent e setDisplay e getActionCommand agent sendSecuredMulticast e getActionCommand
7. Fy public Tester super Starts the application AY public static void main java lang String args int NUMCLIENTS 3 int cPort 3000 starting port address int sPort 5000 String host Thread server Thread clients new Thread NUMCLIENTS try host InetAddress getLocalHost getHostName System out printin Starting Server Agent on host host server new Thread new ServerAgent Server sPort Server server start for int i 0 i lt clients length i System out printin Starting Client Agent i 1 clients i new Thread new ClientAgent Client i 1 cPort i host sPort Client i 1 clients i start while true catch UnknownHostException e System out printin Unknown Host Exception when starting ClientAgent 31 WindowDestroyer package ksu cis momtest import java awt import java awt event ae on Fy public class WindowDestroyer extends WindowAdapter ae public void windowClosing WindowEvent e System exit 0 This type was created in VisualAge This method was created in VisualAge 32 File Sharing Example The File Sharing example consists of client agents who want to request files from the server and the server agents who are responsible for sending files The scenario starts by each start joi
8. i Define a state variable initialized to state 0 ii If it is an initiator conversation create a connection with the agent of interest iii Create a switch statement within a while loop where each case in the switch statement corresponds to a state or a transition Ensure at least one of the states exits the while loop iv Close the connection 5 Create any supporting classes for things such as a Objects that combine multiple parameters into a single object b System setup testing routines c Components of intelligent agents 6 Examples 19 Register Deregister Example ClientA gent package ksu cis momtest import java awt import java awt event import java io import java net import afit mom This type was created in VisualAge ae public class ClientAgent extends Agent implements ActionListener private TextArea theText private Panel textPanel private TextField Tname public String serverHost public int serverPort ClientAgent constructor comment Hf public ClientAgent String agentName int agentPort String sHost int sPort super agentName agentPort sHost the Host to connect to sPort the Port to connect to this serverHost this serverPort server initialization MessageHandler h new MessageHandler this port this h start window initialization setSize 400 300 set default size amp height of new window addWindow
9. isDone true catch UnknownHostException e parent write Unknown Host exception in Client_Register catch EOFException oef parent write Server terminated connection in Client_Register catch IOException e parent write IO Exception in Client_Register 48 ServerReturnFile package ksu cis example FileSharing import ksu cis mom import java net import java io Unicast Conversation initiator to the requesti author Chairoj as public class Serve private ServerAgent parent private String fileName private String client public ServerReturnFile ServerAgent agent String client String file super agent client parent agent fileName file this client cli Lent parent write cli Lent is public void run Message m new Message int state 0 boolean notDone try parent w true rReturnFile rite ConnectionHost is It basically sends the file back ng Gli ent using unicast conversation Mekprasertvit extends Conversation agent port client F connectionHost connection new Socket connectionHost connectionPort output new ObjectOutputStream connection getOutputStream output flush input new ObjectInputStream connection getInputStream while notDone switch state case 0 m performative
10. Key k String algorithm super a group port a secure_multicast_queue k algorithm parent a this gui gui this mesg m public void run Message m new Message int state 0 boolean notDone true try while notDone switch state case 0 m performative display m content this mesg startConversation m conversation_name SecureMulticastReceive state 1 break case 1 notDone false break catch IOException e parent write IO Exception in secured multicast conversation 67
11. Thread new Server_Unregister server input output this m t start start new thread else System out printin xx Invalid Attempt to start new conversation with performative m performative from m sender 24 t new Thread new Sorry server input output this m t start start new thread catch ClassNotFoundException cnfex System out printin ClassNotFoundException catch IOException cnfex System out printin IOException on port ServerAgent receiveMessage This method was created in VisualAge protected void remove_service String agent String service String host int port java util Enumeration enum this registrants elements Registration v while enum hasMoreElements v Registration num nextElement if v agent equals agent amp amp v service equals service amp amp v host equals host amp amp v port port this registrants removeElement v This method was created in VisualAge Ky public void run theText append Starting Server n setVisible true This method was created in VisualAge Xe protected void write String s this theText append s n 25 Client_Register package ksu cis momtest This type was created in VisualAge ay import java net import java io import afit mom public
12. conversations to work with either agents or components as their parents Class that inherits from this class must implement the sendInternal method The MomObject consists of 9 attributes as shown below MomObject parent reference to other MomObject type It is used by the Component class so that conversation classes can work with either agents or components as their parents String name agent name int port unicast port number int multicast_port array of multicast port number int broadcast_port broadcast port number int secure_unicast_port secured unicast port number int secure_multicast_port array of secured multicast port number InetAddress group array of multicast address InetAddress broadcast_address broadcast address The user does not need to know the details of this class since this class does not provide any service and it is used within only within the agentMom package Please refer to the Component Design document for more detail on this class 4 2 Agent Class The Agent class is an abstract class that defines the minimum requirements for an agent to use agentMom package This class inherits the MomObject class It also implements Runnable interface to be runnable as a separate thread which requires a run method Notice that run method is an abstract method so the sub class of this class must implement this method If the agent based architecture is used the run method is where the agen
13. found file ByteArrayOutputStream bs new ByteArrayOutputStream FileInputStream in new FileInputStream fileName int c while c in read 1 bs write c byte b bs toByteArray InfoObject info new InfoObject fileName b m content info 49 this sendMessage m output state 1 break case 1 m this readMessage input if m performative equals ack parent write Client has received the file else parent write ERROR did not get reply back notDone false break input close output close connection close catch UnknownHostException e parent write Unknown Host exception in unicast e toString catch EOFException oef parent write kk Server terminated connection in unicast oef toString catch IOException e parent write IO Exception in unicast e toString 50 Key Distribution Example The Key Distribution example consists of distributor agents who want to distribute the private key used for encrypting and decrypting multicast message and the client agents who are waiting to form the multicast group using secured multicast conversation The scenario starts by distributor agent sends broadcast message asking for IP address The client agents then send back their IP using broadcast conversation Distributor agent waits for a specific time period befor
14. live group packetSize mh start There are two constructors for this class The difference is that the second constructor allows specifying the buffer size of received multicast message The first constructor has a default of 1024 bytes of buffer size Be aware that the buffer size of received message must be equal or greater to the sent message Both constructors have the same first four parameters The four parameters are a pointer to the parent agent object port number time to live of the multicast message and the multicast group address Note that the multicast address is actually a class D IP addresses that is in the range 224 0 0 0 to 239 255 255 255 And the time to live of the message is in the range of 0 255 The table below roughly shows the scope for a given range of time to live TIL Scope 0 32 Institution 33 64 Region 65 128 Continent 10 However this is not always true because the network may refuse to forward the message and message may be dropped by the network router because the multicast socket use an unreliable protocol Basically we use the multicast handler the same way as we use the MessageHandler class When MulticastHandler class is created it starts the multicast socket on the indicated port and joins to specified multicast group Then it automatically sends a multicast message to the group indicating that this agent has join the group When a MulticastHandler receives the message indicating t
15. otherwise the message may be delivered as broadcast message or not delivered at all Also the operating systems must be configured to accept multicast message 4 8 SecureMulticastHandler Class The SecureMulticastHandler is used to handle secured multicast connection from other agents Basically it performs the same functionality as the MulticastHandler class with security service The difference is that this class use symmetric key algorithm to perform message encryption and decryption An agent can create this class as shown below SecureMulticastHandler smh new SecureMessageHandler this port time to live group key algorithm smh start or SecureMulticastHandler smh new SecureMessageHandler this port time to live group packetSize key algorithm smh start Detail of this class is almost the same as the MulticastHandler However there are two more parameters required in the constructors key and algorithm The key parameter is the Key class in the java Security package It stores the private key used for encrypting and decrypting message Notice that we use the same key to encryption and encryption The algorithm parameter is the name of algorithm used to generate the key and how to perform encryption and decryption Thus all agents in this multicast group need to have 11 the same key and algorithm There are many ways to distribute the key For example agents can request the private key from a trust server using
16. Applying Broadcasting Multicasting Secured Communication to agentMom in Multi Agent Systems User s Manual Version 1 0 This document is submitted in partial fulfillment of the requirements for the degree MSE Chairoj Mekprasertvit CIS 895 MSE Project Kansas State University Spring 2004 Using agentMom 1 Introduction What is agentMom agentMom is a framework upon which distributed multiagent systems can be developed It is implemented in Java and provides the basic building blocks for building agents conversations between agents and the message that are passed in the conversations agentMom is capable of using five different type of conversations 1 Unicast conversation using TCP IP This is basically a one to one communication 2 Secured unicast conversation using Secure Socket Layers SSL over TCP IP 3 Multicast conversation using multicast socket and datagram packet With multicast conversation an agent is capable of sending a message to a group of agents that subscribes to the same multicast group 4 Secured multicast conversation using multicast socket and datagram packet with symmetric key algorithm 5 Broadcast conversation using datagram socket and datagram packet With broadcast conversation an agent is capable of sending a message to all agents within the same local network An overview of how conversations in agentMom work is shown below An agent allows itself to speak with other agents by starting a c
17. Fact createSocket connectionHost connectionPort output new ObjectOutputStream connection getOutputStream input new ObjectInputStream connection getInputStream output flush while notDone switch state case 0 m performative GetKey m content key sendMessage m output gui setDisplay Distributor sent key to connection getInetAddress getHostName state 1 break case 1 m readMessage input if m performative equals ack gui setDisplay m sender has received the key notDone false else parent write Error did not get reply back 65 break input close output close connection close catch EOFException oef parent write Server terminated connection in DistributorSendKey catch IOException e parent write IO Exception in DistributorSendKey end run method end class DistributorSendKey 66 SecureMulticastSend package ksu cis example KeyDistribution import java net import java io import java security import ksu cis mom public class SecureMulticastSend extends SecureMulticastConversation private ClientAgent parent private ClientAgentGUI gui private String mesg private String conversation_name SecureMulticastSend public SecureMulticastSend ClientAgent a int port InetAddress group String m ClientAgentGUI gui
18. Listener new WindowDestroyer setTitle this name name the window setBackground Color red setLayout new BorderLayout text panel textPanel new Panel theText new TextArea 12 50 theText setBackground Color white theText setForeground Color black textPanel add theText add textPanel Center top label Panel namePanel new Panel namePanel setForeground Color white Label nameLabel new Label Enter text of your choice namePanel add nameLabel Center add namePanel North This method was created in VisualAge public void actionPerformed ActionEvent e if e getActionCommand equals Exit 20 System exit 0 else theText setText Error in memo interface textPanel repaint This method was created in VisualAge x7 public String get_service if this name equals Client 1 return Laundry if this name equals Client 2 return Dry Cleaning if this name equals Client 3 return Drill Press Operator else return Unknown This method was created in VisualAge Hef public static void main String args String serverHost int serverPort 5000 try serverHost InetAddress getLocalHost getHostName ClientAgent s new ClientAgent Client 3000 serverHost serverPort s run s catch UnknownHostException e System out printi
19. Stream i ObjectOutputStream o ServerAgent a Message ml super s i O a ml parent a public void run int state 0 boolean notDone true parent write Got gt gt m getPerformative m getContent from m getSender set up conversation try while notDone switch state case 0 state 1 break case 1 parent remove_service m sender String m content m host m port parent printRegistrants state 2 break case 2 m setPerformative reply m setContent OK sendMessage m output notDone false break input close output close connection close catch UnknownHostException e parent write Unknown Host exception catch EOFException oef parent write Server terminated connection catch IOException e parent write IO Exception e printStackTrace 29 Registration package ksu cis momtest This type was created in VisualAge ay public class Registration String agent String host int port String service Registration constructor comment Ad public Registration String a String h int p agent a host h port p service ser 30 String ser Tester package ksu cis momtest This type was created in VisualAge EJ import java net public class Tester Tester constructor comment
20. Thread srf t start if not found then ask the group who has it else String client server getInetAddress getHostName ServerMulticast sm new ServerMulticast this multicastPort 0 group 0 String m getContent t new Thread sm testart y gt while sm getDone try Thread sleep 1000 catch InterruptedException iex write ServerRespondRequest InterruptedException end if else write Unrecognized Performative IGNORED catch ClassNotFoundException cnfex catch IOException ioex System out printin IOException in this name find the file when receive a muulticast conversation ag public void receiveMulticastConversation MulticastSocket mSocket Message m Vector multicast_queue Thread t 44 client System out printin Class not found exception in this name if m performative equals find file check if this agent has the file then send back InfoObject info InfoObject m content boolean found this findFile info getFileName if found ServerReturnFile srf new ServerReturnFile this info getClient info getFileName t new Thread srf t start else write File not found on this agent else write Unrecognized Performative IGNORED public boolean findFile String fileName S
21. age java DistributorAgentGUI lt name gt lt broadcast address gt System exit 1 String name args 0 String broadcastAddress args 1l DistributorAgentGUI gui new DistributorAgentGUI name broadcastAddress gui addWindowListener new WindowAdapter public void windowClosing WindowEvent e System exit 0 i gui startUIl end of main method 62 DistributorRequestRegister package ksu cis example KeyDistribution import ksu cis mom import java net import java io public class DistributorRequestRegister extends BroadcastConversation private DistributorAgent parent private String conversation_name private DistributorAgentGUI gui public DistributorRequestRegister DistributorAgent agent int b_port InetAddress broadcast_address DistributorAgentGUI gui super agent broadcast_address b_port agent broadcast_queue this parent agent this conversation_name DistributorRequestRegister this gui gui public void run Message m new Message int state 0 boolean notDone true int count 0 try while notDone switch state case 0 m performative register startConversation m conversation_name ClientReturnRegister state 1 break case 1 try gui setDisplay Agent will wait for reply for 5000 millisec Thread sleep 5000 gui setDisplay 5000 milisec is over catc
22. are originated from the run method in agent class In the second architecture as shown in Figure b an agent consists of one or more components and the conversations belong to components not directly to agents Also an agent can have multiple components and components can have multiple conversation The difference from the first architecture is that component is responsible for making conversation with other agents In the first architecture agents are directly responsible for controlling the conversation Having components separately from agent allows developers to map the agent role s tasks to the component From now we will refer to the first architecture as agent based architecture and the second architecture as component based architecture 3 Requirements for using agentMom 3 1 agentMom package 3 2 java 1 4 is needed in order to use SecureUnicastHandler SecureUnicastConversation SecureMulticastHandler SecureMulticastConversation class java 1 2 or higher is required if the security features are not used 3 3 truststore keystore and certificate files are needed in order to use SecureUnicastHandler and SecureUnicastConversation class details on how to create these files are in section 4 of this chapter 3 4 Multicast supported router is required in order to use multicast capability in agentMom 4 agentMom Package 4 1 MomObject Class MomObject is an abstract class that both Agents and Components inherit from It allows
23. as created in VisualAge EJ import java net import java io import afit mom public class Server_Register extends Conversation ServerAgent parent override parent public Server_Register Socket s ObjectInputStream i ObjectOutputStream o ServerAgent a Message ml super s i O a ml parent a public void run int state 0 boolean notDone true parent write Got gt gt m getPerformative m getContent from m getSender set up conversation try while notDone switch state case 0 parent add_service m sender String m content m host m port parent printRegistrants state 1 break case 1 m setPerformative reply m setContent OK sendMessage m output notDone false input close output close connection close catch UnknownHostException e parent write Unknown Host exception catch EOFException oef parent write Server terminated connection catch IOException e parent write IO Exception Server_Register e printStackTrace 28 Server_Unregister package ksu cis momtest This type was created in VisualAge EJ import java net import java io import afit mom public class Server_Unregister extends Conversation ServerAgent parent override parent public Server_Unregister Socket s ObjectInput
24. castConversation and seven concrete classes MessageHandler SecureUnicastHandler MulticastHandler SecureMulticastHandler BroadcastHandler Message and Sorry The agentMom and example source codes are included in the CD with this document Examples can also be found at the end of this chapter MomObject SecureUnicastHandler gA x 0 Agent MulticastHandler 14 1 0 2 at BroadcastHandler SecureMulticastHandler 0 O MessageHandler NS 0 4 SecureMulticastConversation 1 0 4 Figure 20 Class diagram new agentMom Note that the name Conversation and MessageHandler are not consistent with the other conversations because we want to the agentMom to be compatible to the older version The previous version of agentMom only has unicast conversation type Conversation class the multicast broadcast and secured conversations were added later Thus the Conversation class can be thought of as the UnicastConversation class and MessageHandler as the UnicastHandler a Agent directly controls conversations b Component controls conversations Figure 21 new agentMom s architecture Furthermore there are two architectures that can be applied to agentMom The first architecture is shown in Figure a In the first architecture agent directly controls the conversations This architecture is very straightforward since conversations belong to agent Basically the conversations
25. class Client_Register extends Conversation ClientAgent parent override parent String service public Client_Register ClientAgent a String hostName int portNum String theService super a hostName portNum parent a service theService public void run Message m new Message int state 0 boolean notDone true parent write Starting Client_Register conversation set up conversation try connection new Socket connectionHost connectionPort output new ObjectOutputStream connection getOutputStream output flush input new ObjectInputStream connection getInputStream while notDone switch state case 0 m performative register m content service sendMessage m output state 1 break case 1 m readMessage input if m performative equals reply notDone false else parent write ERROR did not get reply back break input close output close connection close catch UnknownHostException e parent write Unknown Host exception in Client_Register catch EOFException oef parent write Server terminated connection in Client_Register catch IOException e parent write IO Exception in Client_Register 26 Client_Unregister package ksu cis momtest This type was created in VisualAge ay import java net import java io im
26. constructor allows specifying the buffer size of received multicast message The first constructor has a default of 1024 bytes of buffer size Be aware that the buffer size of received message must be equal or greater to the sent message Both constructors have the same first three parameters The three parameters are a pointer to the parent agent object port number and the broadcast address In general broadcast address is in the form Xxxx xxx xxx 255 for local broadcast However many networks do not allow the use of broadcast and they may have a specific address for broadcasting Users have to check the availability of this address After this class is initialized it waits for a message from other agents When broadcast handler receives a message it will check whether the message is a start of new conversation If it is a start of conversation the BroadcastHandler simply calls the parent agent s receiveBroadcastConversation method with the datagram socket received message and broadcast message queue The agent then verifies the received message and starts an appropriate conversation If the received message is for any broadcast conversation class it adds the message to the broadcast message queue Then the broadcast conversation class can get the message from this queue later 12 4 10 Conversation The Conversation class is an abstract class that actually carries out the message passing between agents using unicast communication The
27. conversation because the destination conversation can then reply to the correct conversation The last parameter is the name of the destination conversation The reason for using the name of conversation is that an agent may have multiple concurrent threads of multicast conversation that use the same multicast group hence sharing the same message queue The originating and destinating conversation are needed Moreover multicast conversation must also pass the name to the readMessage method to fetch the message destined for this conversation In 15 this case the multicast is the name of this conversation and MulticastServer is the name of the destination conversation As same as any conversation class in agentMom there re two methods for fetching message from the queue One is a blocked read readMessage and another one is nonblocked read nonblockedReadMessage However the nonblocked read in multicast allows specifying the timeout in milliseconds Be aware that the conversation needs to know how many times it has to perform read message because this is one to many conversation The conversation may receive more than one reply message so the read message also need to perform more than one times Thus it may get an unexpected message if the read message does not perform properly 4 12 SecureMulticastConversation The SecureMulticastConversation class is an abstract class that actually carries out the message passing between agents in the g
28. ctionPort output new ObjectOutputS tream connection getOutputS tream input new ObjectInputStream connection getInputStream After we initialize the connection output input we can then use these variables as same as we do in the Conversation class To exit the conversation we also do the same way as in the Conversation class as shown below input close output close connection close 4 14 BroadcastConversation The BroadcastConversation class is an abstract class that actually carries out the message passing to all agents under the same local network The BroadcastConversation class uses the DatagramSocket to send and receive message In fact the DatagramSocket 16 class is a super class of the MulticastSocket class Detail on using broadcast conversation is the same as in multicast conversation As same as multicast conversation the BroadcastHandler is needed to start first Below is how the conversation can call the super class constructor of the initiator side super agent broadcastAddress port messageQueue An example of the while loop in broadcast conversation initiator s run method can be created as shown below while notDone switch state case 0 m performative calculate m content command1 startConversation m conversation_name BroadcastServer state 1 break case 1 m readMessage broadcast if m performative equals reply parent write String m conte
29. e starts sending the private key using secured unicast conversation to the agents that reply back within the time period After the key is received the client agents form the multicast group and communicate using secured multicast conversation based on the received private key 51 ClientAgent package ksu cis example KeyDistribution 3003 import java io import java net import java security import javax net ssl import ksu cis mom import java util public class ClientAgent extends Agent public static final int unicastPort 3000 public static final int secureUnicastPort 3001 public static final int multicastPort 3002 public static final int broadcastPort 3004 public static final int secureMulticastPort private ClientAgentGUI gui private Key key private String algorithm private SecureMulticastHandler smh public ClientAgent String name super name unicastPort multicastPort broadcastPort secureUnicastPort secureMulticastPort this gui gui try super group super group 0 super group 1 new InetAddress 5 InetAddress getByNam InetAddress getByNam String broadcastAddress 3005 3006 ClientAgentGUI gui 239 299 190 101 239 299 190 712 broadcastAddress super broadcast_address InetAddress getByNam catch Throwable e write Invalid Internet Address BroadcastHandler bh new BroadcastHandler thi
30. e that this message is sent to String inreplyto null The expected label in a reply String language null Name of representation language of the content String ontology null Name of the ontoloty used in the content String performative null Describe the action that the message intends The user can define any performative they feel are necessary int port 0 Port number used for the message String receiver null Name of the receiver String replywith null Whether the sender expects a reply and if so a label for the reply String sender null Name of the sender agent s name When a conversation calls the sendMessage method it automatically fill the sender host and port fields using the parent agent s name and port attributes and automatically gets the host name from the system The replywith and inreplyto fields are also automatically fill if the sendMessage is called from MulticastConversation SecureMulticastConversation and BroadcastConversation The other fields of interest in an agentMom message are the performative and content fields The performative field describes the action that the message intends and is used in the agent and conversation classes to 1 Determine the type of conversation being requested and 2 To control the execution of a conversation in the run method Because agentMom does not have any specific performative types users can define any performative they feel are necessary The co
31. exit 0 else theText setText Error in memo interface 23 textPanel repaint This method was created in VisualAge oi protected void add_service String agent String service String host int port this registrants addElement new Registration agent host port service This method was created in VisualAge public static void main String args ServerAgent s new ServerAgent Server 5000 ssrun This method was created in VisualAge aif protected void printRegistrants java util Enumeration enum this registrants elements Registration v enum this registrants elements while enum hasMoreElements v Registration num nextElement this theText append lt v agent v service v host v port gt n receiveMessage method comment ay public void receiveMessage Socket server ObjectInputStream input ObjectOutputStream output int iy Message m Server_Register s Thread t define all possible conversations receivable here try m Message input readObject this theText append Received message m performative from m sendert n if m performative equals register t new Thread new Server_Register server input output this m t start start new thread else if m performative equals unregister t new
32. gister setContent Object ip try sendMessage register conversation_name DistributorRequestRegister gui setDisplay Agent sends register IP ip getHostAddress System out printin Agent sends register IP ip toString catch IOException ioex parent write ioex toString notDone false break end switch end while end run method end class 58 DistributorA gent package ksu cis example KeyDistribution import java io import java net import java security import javax net ssl import javax crypto import ksu cis mom import java util public class DistributorAgent extends Agent public static final int unicastPort 3000 public static final int secureUnicastPort 3001 public static final int multicastPort 3002 3003 public static final int broadcastPort 3004 public static final int secureMulticastPort 3005 3006 private Vector clientList private DistributorAgentGUI gui private Key key private String algorithm private boolean alive private boolean finishRegister public DistributorAgent String name String broadcastAddress DistributorAgentGUI gui super name unicastPort multicastPort broadcastPort secureUnicastPort secureMulticastPort this gui gui this alive true this clientList new Vector 10 this finishRegister false try super gr
33. h InterruptedException e System out printin e toString state 3 break case 3 do m nonblockedReadMessage DistributorRequestRegister if m content equals timeout parent write TIMEOUT BROADCAST break 63 1000 if m performative equals register parent addToList InetAddress m content m content toString is being this gui setDisplay IP registered while m content equals timeout notDone false parent setFinishRegister true break catch IOException e parent write IO Exception in DistributorRegisterRequest conversation 64 DistributorSendKey package ksu cis example KeyDistribution import ksu cis mom import javax net ssl import java net import java security import java io public class DistributorSendKey extends SecureUnicastConversation private DistributorAgent parent private Key key private DistributorAgentGUI gui public DistributorSendKey DistributorAgent agent InetAddress ip int su_port Key key DistributorAgentGUI gui super agent ip getHostAddress su_port parent agent this key key this gui gui public void run Message m new Message int state 0 boolean notDone true try SSLSocketFactory sslFact SSLSocketFactory SSLSocketFactory getDefault connection SSLSocket ssl
34. he join it calls the receiveMulticastJoin method in agent class Agent has to override this method to make use of it For example agent can keep track of the other agents who join the group after itself The same thing applies to the receiveMulticastLeave method in the Agent class When the sendLeave method in the MulticastHandler class is executed It automatically sends message leave to the group and then unsubscribes from multicast group After this class is initialized it waits for a message from other agents When multicast handler receives a message it will check whether the message is a start of new conversation join leave conversation message If it is a start of conversation the MulticastHandler simply calls the parent agent s receiveMulticastcastConversation method with the multicast socket received message and multicast message queue The agent then verifies the received message and starts an appropriate conversation If the received message is for any multicast conversation class it adds the message to the multicast message queue Then the multicast conversation class can get the message from this queue later If the join or leave message is received it calls the parent agent s receiveMulticastJoin or receiveMulticastLeave as described above Moreover the agent may leave the group by calling the method sendLeave in the MulticastHandler class Note that to properly using multicast protocol the network router does need to support it
35. ibutor sends secured unicast to all agents im the List init new Thread new DistributorSendKey this InetAddress clientList elementAt i secure_unicast_port key gui 60 init start gui setDisplay Sending key to clientList elementAt i toString state 3 break case 3 try gui setDisplay Agent go to sleep before exit Thread sleep 10000 if finishRegister true System exit 0 else state 3 System exit 0 catch InterruptedException e System out println e toString break 61 DistributorAgentGUI package ksu cis example KeyDistribution import java awt import java awt event public class DistributorAgentGUI extends Frame private TextArea display private DistributorAgent agent public DistributorAgentGUI String name String broadcastAddress super Please Wait setLayout new BorderLayout display new TextArea add display Center display setBackground Color white display setForeground Color black setSize 300 200 setVisible true show agent new DistributorAgent name broadcastAddress this Thread t new Thread agent t start public void startUI setTitle Demo III agent name public void setDisplay String m display append m n System out printin m public static void main String args if args length 2 System out printin Us
36. ing software Finally we import the certificate into a new truststore CAj2sdk 1 4 2 gt keytool import file certificate keystore truststore Enter keystore password xxxxxx Owner CN chairoj mekprasertvit OU ksu O cis L manhattan ST ks C us Issuer CN chairoj mekprasertvit OU ksu O cis L manhattan ST ks C us Serial number 402cb4ae Valid from Fri Feb 03 05 27 42 CST 2004 until Thu May 03 06 27 42 CDT 2004 Certificate fingerprints MDS E7 87 63 4E 2F 04 FA 3A 15 92 31 70 4F BO 1F C4 SHA1 94 17 E2 0D 00 DE 09 A7 DA 6A 3E 68 83 FC 39 68 D7 02 25 6E Trust this certificate no yes Certificate was added to keystore Notice that the certificate is valid only a period of time 3 months Now we can then run the class using SSL as shown below java Djavax net ss keyStore keystore Djavax net ss keyStorePass word xxxxxx Djavax net ssl trustStore truststore Djavax net ssl trustStorePassword xxxxxx agentTest 4 7 MulticastHandler Class MulticastHandler is responsible for initializing and starting multicast socket including joining leaving multicast group In generally it handles multicast connection with other agents It uses the MulticastSocket class to subscribe to multicast group When an agent is created it needs to create a new multicast handler thread as shown below MessageHandler mh new MulticastHandler this port time to live group mh start or MessageHandler mh new MulticastHandler this port time to
37. is a pointer to the parent agent The group port and messageQueue parameter are the multicast address port for multicast and multicast message queue respectively Note that the multicast message queue must be a pointer to the same queue as the one the agent passes to the MulticastHandler s constructor An example of multicast conversation initiator s run method can be created as shown below public void run Message m new Message int state 0 boolean notDone true try while notDone switch state case 0 m performative calculate m content command 1 startConversation m conversation_name MulticastServer state 1 break case 1 m readMessage multicast if m performative equals reply parent write String m content from m sender n m performative good bye m content command2 sendMessage m notDone false else parent write ERROR did not get reply back catch IOException e parent write IO Exception in multicast conversation Notice that the startConversation method is used on case 0 This is how multicast conversation can be started Any subsequence will use sendMessage instead as shown in case 1 Also there are three required parameters for sending a message The first one is the Message object The second one is the name of this conversation the name of the conversation must be unique from the other multicast
38. kInternal is a method for fetching a message from the internalMessage queue The sendInternal method allows the component to communicate with other components within an agent This method simply broadcast message to all active components within the agent 4 5 MessageHandler Class The MessageHandler class used to handle unicast connection from other agents When an agent is created it needs to create a new message handler thread as shown below MessageHandler h new MessageHandler this port this h startQ Two parameters are required to create this class The two required parameters are the port number and a pointer to the parent agent object When started the message handler starts a socket server on the indicated port and waits for a connection from another agent When a connection is received the message handler calls the parent agent s receiveMessage method with the connection and the input and output streams Thus agent needs to implement the recetveMessage method and starts an appropriate conversation as described in the Agent class 4 6 SecureUnicastHandler Class The SecureUnicastHandler is used to handle secured unicast connection from other agents Basically it performs the same functionality as the MessageHandler class with security service The difference is that this class use Secure Socket Layers to handle secured communication over the TCP IP connection An agent can create this class as shown below SecureUnicastHandle
39. ln Invalid Attempt to start new conversation with performative m performative from m sender t new Thread new Sorry server input output this m t start start new thread catch ClassNotFoundException cnfex System out println ClassNotFoundException catch IOException cnfex System out println IOException on port ServerAgent receiveMessage In this case after the recetveMessage method reads the message using the m Message input readObject method call the performative of the message is checked to see if it is either register or unregister In this case these are the only two performatives the agent can recognize that start conversations in which it can participate If it is either of these performatives its creates a new conversation object as a new thread sends it the initial message and starts it running using the conversation s run method If the message received does not start with a recognizable performative the agent starts the default Sorry conversation which simply sends a sorry message in reply to the performative Another example the receive MulticastConversation method for multicast conversation can be overridden as shown below public void receiveMulticastConversation MulticastSocket mSocket Message m Vector multicast_queue int 1 Server_Register s Thread t write Received message m performative from
40. m After the connection is made the method enters a while loop that iterates until the conversation is completed Inside the while loop is a simple switch statement that has a case for each possible state of the conversation Actually the state in the run method may or may not correspond one to one with the states of the conversation as defined in a MaSE conversation diagram Actually it is possible to have one state for each state in the diagram plus a state for each transition out of a state In a simple conversation such as the Client_Register conversation this could be modeled as a simple sequence of statements however in the general case conversations may have loops and many branches out of a single state thus the switch within a loop provides the most general mechanism for modeling conversation states The loop and switch statement are shown below while notDone switch state case 0 m performative register m content service sendMessage m output state 1 break case 1 m readMessage input if m performative equals reply notDone false else parent write ERROR did not get reply back break 13 In the code above the state variable starts at state zero In state 0 the message performative is set to register and the message content is set to a string sent to the conversation by the ClientAgent when it was initialized Actually the content of a message can take any Java object type b
41. mport java io Unicast conversation initiator It basically send a request for file and waiting for the accept messag author Chairoj Mekprasertvit ey public class ClientRequestFile extends Conversation private ClientAgent parent private ClientAgentGUI gui private String fileName private String serverName public ClientRequestFile ClientAgent agent String server String req ClientAgentGUI gui super agent server agent port parent agent fileName req serverName server this gui gui see java lang Runnable run Ez public void run Message m new Message int state 0 boolean notDone true try connection new Socket connectionHost connectionPort output new ObjectOutputStream connection getOutputStream output flush input new ObjectInputStream connection getInputStream while notDone switch state case 0 m performative find file m content fileName this sendMessage m output state 1 break case 1 m this readMessage input if m performative equals reply gui setDisplay The request is m content toString else 40 parent write ERROR did not get reply back notDone false break input close output close connection close catch UnknownHostException e parent write Unknown Host exception in unicast e toSt
42. n Host Exception when starting ClientAgent receiveMessage method comment Fy public void receiveMessage Socket server ObjectInputStream input ObjectOutputStream output int i Message m Server_Register s Thread t define all possible conversations receivable here try m Message input readObject System out printin xx Invalid Attempt to start new conversation with performative m performative from m sender t new Thread new Sorry server input output this m t start start new thread catch ClassNotFoundException cnfex System out printin ClassNotFoundException catch IOException cnfex System out printin IOException on port ServerAgent receiveMessage 21 This method was created in VisualAge public void run Thread init theText append Starting Client n setVisible true init new Thread new Client_Register this serverHost serverPort get_service start conversation init start int j for int i 0 i lt 10000000 i Oe ee init new Thread new Client_Unregister this serverHost serverPort get_service start conversation init start This method was created in VisualAge aA protected void write String s this theText append s n 22 ServerAgent package ksu cis momtest import ja
43. n close catch EOFException eof parent write Server terminated connection in SSL catch IOException e parent write IO Exception in SSL 56 ClientReturnRegister package ksu cis example KeyDistribution import ksu cis mom import java net import java io import java util author Chairoj Mekprasertvit ag public class ClientReturnRegister extends BroadcastConversation private ClientAgent parent private ClientAgentGUI gui private String conversation_name ClientReturnRegister public ClientReturnRegister DatagramSocket dSocket Vector queue ClientAgent a int b_port Message m ClientAgentGUI gui super a a broadcast_address b_port queue m this gui gui this dSocket dSocket parent a lt p gt Run method Broadcast IP address of itself when received broadcast request to register see java lang Runnable run a public void run boolean notDone true InetAddress ip null int state 0 int result 0 while notDone switch state case 0 try ip InetAddress getLocalHost System out printin ip getHostAddress state 1 catch UnknownHostException e System out printin Unknowhost Exception in ClientReturnRegister break case 1 Message register new Message 57 register setPerformative register re
44. ning the same multicast group The client agents can request a file by sending a unicast request to any server agent in multicast group If that server agent does not have the file it then sends multicast to the group to send the file instead In this scenario we assume that each server contains files different from the others so there is only who actually sends the file Also the client agent always request existing files because the client agent do not get any answer if the file is not found in the group 33 ClientAgent package ksu cis example FileSharing import java io import java util import ksu cis mom import java net Client agent class This agent request a file from server agent author Chairoj Mekprasertvit 7 public class ClientAgent extends Agent private int state 0 private boolean alive true public static final int unicastPort 3000 private ClientAgentGUI gui public ClientAgent ClientAgentGUI gui super ClientAgent unicastPort this gui gui this port unicastPort MessageHandler h new MessageHandler unicastPort this h start The performative that this agent can participate is found file Other performatives will be ignored e 7 public void receiveMessage Socket server ObjectInputStream input ObjectOutputStream output Thread t Message m try m Message input readObject if m performative equals found file
45. nnection There are really two types of conversation classes that can be derived from the MulticastConversation class one for the conversation initiator and one for the conversation respondent The basic difference lies in which constructor is used and the details in the abstract run method which must be implemented in the concrete class derived from the MulticastConversation class Detail on how to create a multicast conversation initiator and respondent is the same as unicast conversation such as using the while loop and switch statement in the run method However the connection of multicast conversation is performed differently There is no need to create a connection socket for sending a message since the MulticastConversation takes care of this MulticastSocket uses connectionless protocol so there is no input and out stream as in the unicast conversation In order to initiate multicast conversation an agent need to start the multicast handler first because the handler is responsible for joming the multicast group and it is also responsible for receiving all multicast messages and place in the message queue The conversation can fetch the message through the message queue by using its conversation name as explained in the next paragraph When the multicast conversation is created the constructor needs to call the super class constructor of the initiator side as shown below super agent group port messageQueue 14 The agent parameter
46. nt from m sender n m performative good bye m content command2 sendMessage m notDone false else parent write ERROR did not get reply back Please be aware that sending many broadcast messages can easily flood the network Also message can be lost or undelivered easily using this type of conversation Below are some of the possible causes 1 The network do not allow broadcast message 2 The broadcast address is incorrect 3 The router drops message especially during busy traffic 4 The packet 4 15 Message Class Message class defines the field used in the message passed back and forth between agents Note that these fields are derived from the fields in a KQML message and some of them are automatically filled by the sendMessage method in each type of conversation classes In agentMom there is no restriction in using these fields For more information about KQML please refer to http www fipa org It is fairly straightforward and consists of the following attributes Object content null Support for complex object that encapsulates a number of attribute types These complex objects can be used to pass multiple parameters in a single message Note that in order to pass an object across a socket connection it must implement the interface Serializable 17 String force null Specify whether the sender will never deny the meaning of the performative String host null Host nam
47. ntent of an agentMom message is also very general Basically the message passes any valid Java object type This can be as simple as a string or a more complex object that encapsulates a number of attribute types These complex objects can be used to pass multiple parameters in a single message as shown in the class below public class ComplexObject implements Serializable String agent String host int port String service public ComplexObject String a String h int p String ser agent a host h port p service ser This class encapsulates four parameters three strings and an integer that can be assigned to message content field Note that in order to pass an object across a socket connection it must implement the interface Serializable 18 Note that in order to pass an object across a socket connection it must implement the interface Serializable 4 16 Sorry Class The Sorry class defines a general purpose conversation to reply Sorry to any unknown unexpected type of unicast conversation It is a simply concrete class of Conversation class so there is no implementation required in this class Automatically performative field is set to sorry and content field is set to unknown conversation request when using this class The example on how to use this class is shown above when we described the Agent class 5 Step By Step Construction To build an application using the agentMom framework you need
48. od and MulticastHandler will call receiveMulticastConversation method when it receives a start of a new conversation from other agents Because the original source of agentMom defines recetveMessage method to be an abstract method all sub class of the Agent class must implement this method However the other types of conversation are optional Users only need to override the receive methods that they want to use These receive methods are an empty method in Agent class However the parameters passing to the methods must be the same as defined in the Agent class Basically users can implement by either reading the message from the connection stream unicast or reading the message directly multicast and broadcast and then determining if it is a valid conversation For example the recerveMessage method for unicast conversation can be implement as shown below public voidreceiveMessage Socket server ObjectInputStream input ObjectOutputStream output int i Message m Server_Register s Thread t try m Message input readObject write Received message m performative from m sender if m performative equals register t new Thread new Server_Register server input output this m t start start new thread else if m performative equals unregister t new Thread newServer_Unregister server input output this m t start Q start new thread else System out print
49. onversation handler that monitors a local port for messages All agent communication is performed via conversation classes which define valid sequences of messages that agents can use to communicate When one agent wants to communicate with other agents it starts one of its conversations as a separate Java thread The conversation then establishes a socket connection with the other agent s message handler and sends the initial message in the conversation When the message handler receives a message it passes the message to the agent s receive message method that compares the message against its known list of allowable message types to see if it is the start of a valid conversation If the conversation is valid the agent starts its side of the appropriate conversation also as a separate Java thread From that point on all communication is controlled by the conversation threads at of each agent The conversations send read messages to from others using built in readMessage and sendMessage methods make J connection amp receive send initial receive message message send read message gt Thread Sub Obiect creation Figure 19 new agentMom 2 How to use agentMom The ksu cis mom package which makes up the basics of agentMom is shown below It consists of nine abstract classes MomObject Agent Component AgentConversation Conversation SecureUnicastConversation MulticastConversation SecureMulticastConversation and Broad
50. oup new InetAddress 5 super group 0 InetAddress getByName 239 255 10 11 super broadcast_address InetAddress getByName broadcastAddress algorithm DES key KeyGenerator getInstance algorithm generateKey catch Throwable e write Invalid Internet Address MessageHandler h new MessageHandler unicastPort this h start MulticastHandler mh new MulticastHandler this multicastPort 0 1 group 0 mh start 59 BroadcastHandler bh new BroadcastHandler this broadcastPort broadcast_address bh start public void receiveMessage Socket server ObjectInputStream input ObjectOutputStream output public void addToList InetAddress ip this clientList addElement ip public void setFinishRegister boolean bool this finishRegister bool see java lang Runnable run public void run int state 0 Thread init while alive switch state case 0 gui setDisplay Distributor sends Broadcast init new Thread new DistributorRequestRegister this broadcastPort new Thread broadcast_address gui init start state 1 break case 1 try Thread sleep 10000 if finishRegister true state 2 else state 1 catch InterruptedException e System out printin e toString break case 2 for int i 0 i lt clientList size i gui setDisplay Distr
51. port afit mom public class Client_Unregister extends Conversation ClientAgent parent override parent String service public Client_Unregister ClientAgent a String hostName int portNum String theService super a hostName portNum parent a service theService public void run Message m new Message int state 0 boolean notDone true parent write Starting Client_Unregister conversation set up conversation try connection new Socket connectionHost connectionPort output new ObjectOutputStream connection getOutputStream output flush input new ObjectInputStream connection getInputStream while notDone switch state case 0 m setPerformative unregister m content service sendMessage m output state 1 break case 1 m readMessage input if m performative equals reply notDone false else parent write ERROR did not get reply back n break input close output close connection close catch UnknownHostException e parent write Unknown Host exception in Client_Unregister catch EOFException oef parent write Server terminated connection in Client_Unregister catch IOException e parent write IO Exception in Client_Unregister e printStackTrace 27 Server_Register package ksu cis momtest This type w
52. r suh new SecureUnicastHandler this port this suh start To create the SecureUnicastHandler it requires two parameters port number and a reference to parent agent object When started the message handler starts a SSL socket server on the indicated port and waits for a connection from another agent When a connection is received the message handler calls the parent agent s receiveSecureUnicastConversation method with the connection and the input and output streams Thus agent needs to implement the receiveSecureUnicastConversation method and starts an appropriate conversation as described in the Agent class The agent then verifies the received message and starts an appropriate conversation SSL uses many cryptography technologies together such as public key private key session key authentication digital signature etc These are transparent to the user of SSL technology Basically SSLSocket and SSLServerSocket can be used almost the same way as Socket and ServerSocket class However the keystore trustore and certificate must be generated on both sides of communications Also each side of communication must have certificate of the other side installed Please note that to be able to use this class java version 1 4 is required For example the tool keytool provided in java version 1 4 packages can be used to generate these requirements An example on how to create is shown at the end of this section
53. re are three methods in the Conversation class readMessage nonblockedReadMessage and sendMessage that actually pass the messages back and forth over the socket connection There are really two types of conversation classes that can be derived from the Conversation class one for the conversation initiator and one for the conversation respondent The basic difference lies in which constructor is used and the details in the abstract run method which must be implemented in the concrete class derived from the Conversation class An example of an initiator conversation class is the Client_Register class in Register Deregister Example To initiate this conversation the ClientAgent creates a new Client_Register object as a separate thread using the Client_Register constructor This constructor does not need to send a socket input stream or output stream see second Conversation constructor in Register Deregister Example since as an initiator the conversation creates a new socket and opens an input and output stream with a second agent s message handler When the ClientAgent starts the Client_Register conversation class the Client_Register s run method is started This method controls the conversation It creates a new connection using the following commands connection new Socket connectionHost connectionPort output new ObjectOutputStream connection getOutputStream output flushQ input new ObjectInputStream connection getInputStrea
54. ring catch EOFException oef parent write xk Server terminated connection in unicast oef toString catch IOException e parent write IO Exception in unicast e toString 41 package ksu cis example FileSharing import java io InfoObject type for the content field of Message class requesting file s name the fil author Chairoj Mekprasertvit ae InfoObject and the requesting agent IP address public class InfoObject implements Serializable private String fileName null private byte file private String client null public InfoObject String f fileName client f C fileName fil b f public String getFileName return fileName public String getClient return client public byte getFile return file String c public InfoObject String f byte b 42 It contains the ServerAgent package ksu cis example FileSharing import java io import java net import java util import ksu cis mom Server agent that has two services get the file request and send file author Chairoj Mekprasertvit ad public class ServerAgent extends Agent public static final int multicastPort 3002 3003 public static final int secureMulticastPort 0 0 public static final int unicastPort 3000 public ServerAgent super ServerAgent unicastPort multicastPort 0
55. roup using secured multicast communication SecureMulticastConversation has the same detail as the MulticastConversation class The agent has to start the SecureMulticastHandler first before starting a secured multicast conversation Also the private key and the name of the must be the same as the SecureMulticastHandler class uses Below is how the conversation can call the super class constructor of the initiator side super agent group port messageQueue key algorithm The details on how to send and receive message can be performed the same way as in the multicast conversation Message encryption and decryption is done automatically 4 13 SecureUnicastConversation The SecureUnicastConversation class is an abstract class that actually carries out the message passing to agents in the same group using secured multicast communication Because this class relies on the SSL technology as same as the SecureUnicastHandler class it has the same requirements as the SecureUnicastHandler class There is only one different between using this class and the Conversation class the socket In the Conversation class the Socket class is used to make connection to the other agents In this class the SSLSocket is used instead The code below shows how to create the SSLSocket class to make a connection with other agents SSLSocketFactory sslFact SSLSocketFactory SSLSocketFactory getDefault connection SSLSocket sslFact createSocket connectionHost conne
56. s bh start SecureUnicastHandler suh new SecureUnicastHandler secureUnicastPort suh start public void receiveMessage Socket server ObjectInputStream input ObjectOutputStream output public void receiveBroadcastConversation DatagramSocket bSocket Message m Vector broadcast_queue Thread t if m performative equals register 52 broadcastPort broadcast_address this t new Thread new ClientReturnRegister bSocket broadcast_queue this broadcastPort m gui t start public void receiveSecureMulticastConversation MulticastSocket mSocket Message m Vector multicast_queue Key k String algorithm System out printin receive multicast gui setDisplay String m content public void receiveSecureUnicastConversation SSLSocket server ObjectInputStream input ObjectOutputStream output Message m Thread t try m Message input readObject if m performative equals GetKey this key Key m content this algorithm key getAlgorithm gui setDisplay Agent has received the secrect key gui setDisplay Key using key getAlgorithm j t new Thread new ClientGetKey server input outpu t start smh new SecureMulticastHandler Lr String m content this m this secureMulticastPort 1 1 group 1 key DES smh start catch
57. sage m new Message int state 0 boolean notDone true try while notDone switch state case 0 m performative find file InfoObject info new InfoObject fileName client m content info startConversation m conversation_name Server state 1 break case 1 notDone true isDone true catch IOException e parent write IO Exception in multicast conversation 46 ServerRespondRequest package ksu cis example FileSharing import java net import ksu cis mom import java io Fx Unicast conversation respondent It basically accepts the request and send the accept request messag author Chairoj Mekprasertvit ay public class ServerRespondRequest extends Conversation private ServerAgent parent private boolean isDone false public ServerRespondRequest Socket s ObjectInputStream i ObjectOutputStream o ServerAgent a Message m super s i O a m parent a public boolean getDone return isDone public void run int state 0 boolean notDone true int result 0 try while notDone switch state case 0 Message reply new Message reply setPerformative reply reply setContent accepted this sendMessage reply output state 1 break case 1 notDone false break input close 47 output close connection close
58. secured unicast conversation An agent can generate a key as shown below algorithm DES key KeyGenerator getInstance algorithm generateKey In this case we use the DES algorithm and then use the KeyGenerator class to generate a random key based on the algorithm used There is no restriction on how an agent obtains the key and algorithm as long as it is the symmetric key algorithm Message encryption and decryption are automatically performed by agentMom package message is encrypted before sending and decrypted after receiving so agent only provides the key and algorithm and make sure that all agents in the group have the same key and algorithm 4 9 BroadcastHandler BroadcastHandler is responsible for initializing and starting datagram socket for broadcast conversation It uses the DatagramSocket class to send and receive broadcast conversation in form of datagram packet When an agent is created it needs to create a new broadcast handler thread to be able to receive a start of broadcast conversation from the other agents When BroadcastHandler is created it starts the DatagramSocket class for broadcast conversation Below is how an agent can start the BroadcastHandler class BroadcastHandler bh new BroadcastHandler this port address bh start or BroadcastHandler bh new BroadcastHandler this port address packetSize bh start There are two constructors for this class The difference is that the second
59. sers of agentMom do not need to know any thing about this class since it does not provide any service 4 4 Component Class The Component class is an abstract class that defines the minimum requirements for a component This class inherits from MomObject class It implements the Runnable interface to be able to run as a thread It requires only one parameter MomObject MomObject is used to be able to refer to the agent that uses this component The idea of Component class is to support agent architecture that component performs different tasks Each component is responsible for particular tasks Thus the agents role s tasks can be mapped to component Also components are responsible for starting the conversation with other agents instead of agent itself Therefore agent starts the components and component starts the conversations There are two important attributes in this class internalMessage and externalMessage Both attributes are a message queue of type Vector used for internal and external communication As the name imply the internalMessage queue is used for communication between components of agent The externalMessage is used for passing message between component class and conversation so the message can be deliver to other agents by conversation class Methods involve with these attributes are checkExternal checkInternal enqueueExternal enqueueInternal and sendInternal These methods are very straightforward For example chec
60. t normally initiates any conversations The agent class provides two main constructors One is for using only unicast conversation This constructor require two parameters name of the agent and the port number for unicast communication on which its unicast message handler MessageHandler class will listen for incoming messages The constructor is shown below public Agent String name int port Another constructor is for using any or all type of conversations The constructor is shown below public Agent String name int unicast_port int multicast_port int broadcast_port int secure_unicast_port int secure_multicast_port It takes six parameters String of agent name integer of port used in each conversation If any port is assigned to be less than one then it indicates that the conversation is not going to be used Note that the arguments multicast_port and secure_multicast_port are an array of integer type It is because we allows agent to subscribe to multiple groups Thus one port is used for one group Assigning the first element less than one indicates that the multicast will not be used For all receive methods receive Message receiveMulticastConversation etc they are used when the handlers MessageHandler MulticastHandler etc receive a start of a new conversation from other agents The handler will call the receive method corresponding to itself For example the MessageHandler will call the receiveMessage meth
61. to perform the following 1 Get a copy of agentMom classes included in the CD with this document 2 Define your agent classes and conversations according the MaSE Multiagent Systems Engineering methodology An environment agentTool is available to help you with this Please note that the current agentTool only supports code generation for unicast conversation 3 For each agent class in your system extend the agentMom Agent class a Define any necessary receive message methods for each type of conversation to handle all conversations for which the agent is a respondent b For each action defined in the set of conversations in which this agent may participate define a method in the agent class This will be your interface to the conversation c Implement the run method as the main procedure of the method If your agent initiates any conversations this could be where they will originate d If you want to run your agent as a stand alone application create a main method to initialize the agent running 4 For each conversation in your system design create two conversation classes in initiator and a respondent class a For each initiator class define a constructor that includes as parameters the first message sent b For each respondent class define a constructor that includes as a parameter the message read by the parent receive conversation method before the conversation thread was started c Implement the run method
62. tring user_dir System getProperty user dir File file new File user_dir String all file list boolean found false for int i 0 i lt xall length i if fileName equals all i found true write The file is found break else found false return found public void run boolean alive true while alive try Thread sleep 1000 catch InterruptedException iex System out printin Thread Interrupted in this name public static void main String args ServerAgent server new ServerAgent Thread t new Thread server t start 45 ServerMulticast package ksu cis example FileSharing import ksu cis mom import java net import java io i EY Multicast conversation initiator It basically sends the multicast request to the group asking to send the file to the client ap public class ServerMulticast extends MulticastConversation private String fileName private String conversation_name private ServerAgent parent private String client private boolean isDone false public ServerMulticast ServerAgent a int port InetAddress group String req String client super a group port a multicast_queue parent a this fileName req this conversation_name ServerMulticast this client client public boolean getDone return isDone public void run Mes
63. ut it must implement the interface Serializable After sending the message the state variable is set to 1 and the break statement takes us out of the switch statement Since notDone is still true we stay in the loop this time entering the case 1 option of the switch statement At this point we wait at the readMessage call until a message comes in from the other agent In this case we use the readMessage method that is a blocking read wait until message arrives There is also a nonblockedReadMessage that allows the read message to timeout thus allowing the conversation to check to see if it has a message without waiting forever The default value of timeout is 100 milliseconds Then if the message is what we expect a reply performative we process it otherwise we print an error message In this case we do nothing with the reply and simply set the notDone variable to false so that we will exit the while loop After exiting the conversation we close the connection with the other agent using the sequence of close statements shown below input close output close connection close 4 11 MulticastConversation The MulticastConversation class is an abstract class that actually carries out the message passing between agents in the group using multicast communication There are two methods in the MulticastConversation class readMessage nonblockedReadMessage and sendMessage that actually pass the messages back and forth over the socket co
64. va util import java awt import java awt event import java net import java io import afit mom This type was created in VisualAge oh public class ServerAgent extends Agent implements ActionListener private TextArea theText private Panel textPanel private TextField Tname private Vector registrants new Vector 25 ServerAgent constructor comment K public ServerAgent String n int p super n p MessageHandler handler server initialization handler new MessageHandler port this handler start window initialization setSize 500 300 set default size amp height of new window addWindowListener new WindowDestroyer create listener setTitle Server name the window setBackground Color blue setLayout new BorderLayout text panel textPanel new Panel theText new TextArea 12 60 theText setBackground Color white theText setForeground Color black textPanel add theText add textPanel Center top label Panel namePanel new Panel namePanel setForeground Color white Label nameLabel new Label Enter text of your choice namePanel add nameLabel Center add namePanel North setVisible true This method was created in VisualAge 7 public void actionPerformed ActionEvent e if e getActionCommand equals Exit System
65. ved author Chairoj Mekprasertvit ef public class ClientReceiveFile extends Conversation private ClientAgent parent private ClientAgentGUI gui private File file public ClientReceiveFile Socket s ObjectInputStream i ObjectOutputStream o ClientAgent a Message m ClientAgentGUI gui super s i O a m parent a this gui gui w public void run int state 0 boolean notDone true try while notDone switch state case 0 InfoObject info InfoObject m content try FileOutputStream out new FileOutputStream info getFileName out write info getFile out close catch IOException ioex parent write Error writing file ioex toString state 1 case 1 Message reply new Message reply setPerformative ack sendMessage reply output gui setDisplay Agent successfully get the file notDone false break 38 input close output close connection close catch UnknownHostException e parent write Unknown Host exception in Client_Register catch EOFException oef parent write Server terminated connection in Client_Register catch IOException e parent write IO Exception in Client_Register end run method end class 39 ClientRequestFile package ksu cis example FileSharing import ksu cis mom import java net i
66. y new TextArea add display Center display setBackground Color white display setForeground Color black add field South setSize 300 200 setVisible true show agent new ClientAgent this Thread t new Thread agent t start create field for outgoing secured multicast message field setEnabled false field addActionListener new ActionListener public void actionPerformed ActionEvent e setDisplay e getActionCommand agent sendRequest e getActionCommand public void startUI field setEnabled true setTitle Demo III agent name setDisplay Client started 36 lt p gt Enable the TextField Allows user to type secured multicast message 7 public void setField field setEnabled true public void setDisplay String m display append m n main method to start the client param args wy public static void main String args ClientAgentGUI gui new ClientAgentGUI gui addWindowListener new WindowAdapter public void windowClosing WindowEvent e System exit 0 i gui startUl end of main method 37 ClientReceiveFile package ksu cis example FileSharing import ksu cis mom import java net import java io Unicast conversation respondent It send an acknowledgement message when th file is recei

User`s Manual - Kansas State University

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