java socket 聊天室

package server; import java.io.*; import java.net.*; import java.util.*; public class Server { // The ServerSocket we'll use for accepting new connections private ServerSocket ss; // A mapping from sockets to DataOutputStreams. This will // help us avoid having to create a DataOutputStream each time // we want to write to a stream. private Hashtable outputStreams = new Hashtable(); // Constructor and while-accept loop all in one. public Server( int port ) throws IOException { // All we have to do is listen listen( port ); } private void listen( int port ) throws IOException { // Create the ServerSocket ss = new ServerSocket( port ); // Tell the world we're ready to go System.out.println( "Listening on "+ss ); // Keep accepting connections forever while (true) { // Grab the next incoming connection Socket s = ss.accept(); // Tell the world we've got it System.out.println( "Connection from "+s ); // Create a DataOutputStream for writing data to the // other side DataOutputStream dout = new DataOutputStream( s.getOutputStream() ); // Save this stream so we don't need to make it again outputStreams.put( s, dout ); // Create a new thread for this connection, and then forget // about it new ServerThread( this, s ); } } // Get an enumeration of all the OutputStreams, one for each client // connected to us Enumeration getOutputStreams() { return outputStreams.elements(); } // Send a message to all clients (utility routine) void sendToAll( String message ) { // We synchronize on this because another thread might be // calling removeConnection() and this would screw us up // as we tried to walk through the list synchronized( outputStreams ) { // For each client ... for (Enumeration e = getOutputStreams(); e.hasMoreElements(); ) { // ... get the output stream ... DataOutputStream dout = (DataOutputStream)e.nextElement(); // ... and send the message try { dout.writeUTF( message ); } catch( IOException ie ) { System.out.println( ie ); } } } } // Remove a socket, and it's corresponding output stream, from our // list. This is usually called by a connection thread that has // discovered that the connectin to the client is dead. void removeConnection( Socket s ) { // Synchronize so we don't mess up sendToAll() while it walks // down the list of all output streamsa synchronized( outputStreams ) { // Tell the world System.out.println( "Removing connection to "+s ); // Remove it from our hashtable/list outputStreams.remove( s ); // Make sure it's closed try { s.close(); } catch( IOException ie ) { System.out.println( "Error closing "+s ); ie.printStackTrace(); } } } // Main routine // Usage: java Server <port> static public void main( String args[] ) throws Exception { // Get the port # from the command line int port = Integer.parseInt( "4331" ); // Create a Server object, which will automatically begin // accepting connections. new Server( port ); } }