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SocketPeer.javaAPI DocExample6712Sat Sep 26 10:07:40 BST 1998jdc.patterns.peer

SocketPeer

public class SocketPeer extends Peer implements Runnable
A peer which connects to other peers using IP sockets. The connection properties required are a host name and port number. Since these uniquely identify a peer on an IP network, they are used as the name and id properties on the peer's identity.

Fields Summary
public static final String
HOST_PROP
Standard connection property names, stored in the remote Peer's Identity
public static final String
PORT_PROP
public static final String
SOCKET_PROP
public static final String
PEER_IN
public static final String
PEER_OUT
public static final String
POLLER
protected ServerSocket
mSocket
Server socket used to listen for remote peers attempting to connect.
Constructors Summary
public SocketPeer(int port)
Create a local socket peer listening on the given port. Giving a port number of zero causes a random free port to be chosen.


                              
       
    mSocket = new ServerSocket(port);
    int assnPort = mSocket.getLocalPort();
    mIdentity = new Identity(assnPort);
    mIdentity.setName(InetAddress.getLocalHost().getHostName());
protected SocketPeer()
Internal constructor, used to create a "degenerate" SocketPeer, used locally to represent remote peers and to hold their connection properties within their identities.

Methods Summary
public voidaddPeer(Peer p)
Add a new Peer. In addition to the default Peer behavior, also create
a MsgPoller for the new Peer, to listen for incoming messages.
    super.addPeer(p);
    try {
      MsgPoller poller = new MsgPoller(p);
      p.getIdentity().setProperty(POLLER, poller);
      poller.start();
    }
    catch (Exception e) {
      System.out.println("Failed to attach poller to " +
			 p.getIdentity().getName() + " " +
			 p.getIdentity().getId());
      e.printStackTrace();
    }
  
public booleanconnect(java.util.Properties connProps)
Connect to a peer given the connection properties. The SocketPeer looks
for a "host" and "port" property in the property list, and attempts a
Socket connection to the remote agent.
    boolean success = false;
    String host = (String)connProps.get(HOST_PROP);
    Integer port = (Integer)connProps.get(PORT_PROP);
    if (host != null && port != null) {
      try {
	Socket peerConn = new Socket(host, port.intValue());
	SocketPeer peer = newPeer(peerConn);
	addPeer(peer);
	success = true;
      }
      catch (Exception e) {
	System.out.println("Error connecting to peer " + host + ":" + port);
      }
    }

    return success;
  
public booleanconnect(java.util.Properties connProps, Identity peerID)
Connect to a peer given the connection properties and identity of the
peer. Subclasses can choose to implement this using both arguments, or
ignoring one in favor of the other (connection properties vs. properties
pulled from the remote peer identifier).
    // If necessary, copy the critical properties from the identity of the
    // remote peer to the connection properties.
    if (peerID.getName() != null && connProps.getProperty(HOST_PROP) == null) {
      connProps.put(HOST_PROP, peerID.getName());
    }
    if (peerID.getId() > 0 && connProps.getProperty(PORT_PROP) == null) {
      connProps.put(PORT_PROP, new Integer(peerID.getId()));
    }

    return connect(connProps);
  
public voidhandle(Message m)
Handle incoming message.
    System.out.println(getIdentity().getName() + "(" + getIdentity().getId() +
		       ") received message " + m);
  
protected static jdc.patterns.peer.SocketPeernewPeer(java.net.Socket s)
Initialize a new SocketPeer with the expected properties.
    SocketPeer peer = null;
    try {
      // Make an identity for the new peer, using the remote port as the ID
      Identity i = new Identity(s.getPort());
      // Use the remote host name as the peer's name
      i.setName(s.getInetAddress().getHostName());
      // Get the in and out streams from the socket
      InputStream in = s.getInputStream();
      OutputStream out = s.getOutputStream();
      // Store the socket and the streams in the identity's property list
      i.setProperty(SOCKET_PROP, s);
      i.setProperty(PEER_IN, in);
      i.setProperty(PEER_OUT, out);
      // Make the new peer and set its identity
      peer = new SocketPeer();
      peer.setIdentity(i);
    }
    catch (Exception e) {
      System.out.println("Failed to initialize peer:");
      e.printStackTrace();
    }

    return peer;
  
public voidrun()
When run within a thread, just listen to server socket for remote peer
connect attempts, and make new peers out of them.
    while (true) {
      try {
	Socket s = mSocket.accept();
	addPeer(newPeer(s));
      }
      catch (Exception e) {
	System.out.println("Error accepting socket connection.");
	e.printStackTrace();
      }
    }
  
public booleansend(Message msg, Identity peerID)
Send the message to the identified peer.
    boolean success = false;
    try {
      OutputStream out = (OutputStream)peerID.getProperty(PEER_OUT);
      ObjectOutputStream oout = new ObjectOutputStream(out);
      oout.writeObject(msg);
      success = true;
    }
    catch (Exception e) {
      System.out.println("Failed to send message to: " + peerID.getName() +
			 ", " + peerID.getId());
      e.printStackTrace();
    }

    return success;