it begins with the copyright statement attached to the code. The first example involves minor modifications of the original code. I have noted those changes in the body of the code. The second example involves more substantial modifications. I have noted those changes by a change in the copyright statement itself. Please follow this "standard" for the code you use in your final projects.
Conceptually, using the ServerSocket class is very simple.
/*
* Cay S. Horstmann & Gary Cornell, Core Java
* Published By Sun Microsystems Press/Prentice-Hall
* Copyright (C) 1997 Sun Microsystems Inc.
* All Rights Reserved.
*
* Permission to use, copy, modify, and distribute this
* software and its documentation for NON-COMMERCIAL purposes
* and without fee is hereby granted provided that this
* copyright notice appears in all copies. */
/*
*
* THE AUTHORS AND PUBLISHER MAKE NO REPRESENTATIONS OR
* WARRANTIES ABOUT THE SUITABILITY OF THE SOFTWARE, EITHER
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
* IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE, OR NON-INFRINGEMENT. THE AUTHORS
* AND PUBLISHER SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED
* BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
* THIS SOFTWARE OR ITS DERIVATIVES.
*/
/**
* @version 1.10 27 Jun 1997
* @author Cay Horstmann
*/
/*
*Some modifications have been made to this code by Jerrold Siegel.
*These modifications are noted as comments in the code itself.
*The modifications have been make in compliance with the original
*Copyright statement above.
*THE AUTHOR OF THESE CHANGES ALSO ASSERTS THE ORIGINAL AUTHOR'S POSITION
*AS TO THE LACK OF REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE SOFTWARE.
*/
import java.io.*;
import java.net.*;
public class ThreadedEchoServer
//J. Siegel: java ThreadedEchoServer is invoked on, say jinx.umsl.edu
{ public static void main(String[] args )
{ int i = 1;
int port_to_listen=8189;//J. Siegel: Use a symbolic reference for the port
try
{ ServerSocket s = new ServerSocket(port_to_listen);
//J. Siegel: Acknowledge that the Server is listening.
System.out.println("Listening on Port "+port_to_listen);
for (;;)
{ Socket incoming = s.accept( );
System.out.println("Spawning " + i);
new ThreadedEchoHandler(incoming, i).start();
i++;
}
}
catch (Exception e)
{ System.out.println(e);
}
}
}
class ThreadedEchoHandler extends Thread
{
private Socket incoming;
private int counter;
public ThreadedEchoHandler(Socket i, int c)
{ incoming = i; counter = c; }
public void run()
{ try
{ BufferedReader in = new BufferedReader
(new InputStreamReader(incoming.getInputStream()));
PrintWriter out = new PrintWriter
(incoming.getOutputStream(), true /* autoFlush */);
out.println( "Hello! Enter BYE to exit." );
boolean done = false;
while (!done)
{ String str = in.readLine();
if (str == null) done = true;
else
{ out.println("Echo (" + counter + "): " + str);
if (str.trim().equals("BYE"))
done = true;
}
}
incoming.close();
}
catch (Exception e)
{ System.out.println(e);
}
}
}
The next example, based on ThreadedEchoServer.java, provides a simple "Chat" server. The code works under the assumption that only two users connect to the chat-server.
/*
* Cay S. Horstmann & Gary Cornell, Core Java
* Published By Sun Microsystems Press/Prentice-Hall
* Copyright (C) 1997 Sun Microsystems Inc.
* All Rights Reserved.
*
* Permission to use, copy, modify, and distribute this
* software and its documentation for NON-COMMERCIAL purposes
* and without fee is hereby granted provided that this
* copyright notice appears in all copies.
*
* THE AUTHORS AND PUBLISHER MAKE NO REPRESENTATIONS OR
* WARRANTIES ABOUT THE SUITABILITY OF THE SOFTWARE, EITHER
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
* IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE, OR NON-INFRINGEMENT. THE AUTHORS
* AND PUBLISHER SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED
* BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
* THIS SOFTWARE OR ITS DERIVATIVES.
*/
/**
* @version 1.10 27 Jun 1997
* @author Cay Horstmann
*/
/*
*This code has been modified by Jerrold Siegel.
*The modifications have been make in compliance with the original
*Copyright statement above.
*THE AUTHOR OF THESE MODIFICATIONS ALSO ASSERTS THE ORIGINAL AUTHOR'S POSITION
*AS TO THE LACK OF REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE SOFTWARE.
*/
import java.io.*;
import java.net.*;
public class ThreadedChatServer
{ public static void main(String[] args )
{ int i = 0;
int port_to_listen_on=8189;
BufferedReader in[]=new BufferedReader[2];
PrintWriter out[]=new PrintWriter[2];
//Two "global" channels are required to cross-connect the two ThreadedChatHandler instances.
try
{ ServerSocket s = new ServerSocket(port_to_listen_on);
System.out.println("Listening on Port "+port_to_listen_on);
for (;;)
{ Socket incoming = s.accept( );
System.out.println("Spawning " + i);
//must pass "in" and "out" since we are not using inner classes.
new ThreadedChatHandler(incoming, i,in,out).start();
i++;
}
}
catch (Exception e)
{ System.out.println(e);
}
}
}
class ThreadedChatHandler extends Thread
{
private Socket incoming;
private int counter;
private BufferedReader in[];
private PrintWriter out[];
public ThreadedChatHandler(Socket i, int c,BufferedReader in[],PrintWriter out [])
{ incoming = i; counter = c;
this.in=in;this.out=out;
}
public void run()
{ int other=(counter==0)?1:0;
String str[]=new String[2];
try
{ in[counter] = new BufferedReader
(new InputStreamReader(incoming.getInputStream()));
out[counter] = new PrintWriter
(incoming.getOutputStream(), true /* autoFlush */);
out[counter].println( "Hello! Enter BYE to exit." );
boolean done = false;
while (!done)
{ str[other] = in[counter].readLine();
if (str[other] == null) done = true;
else
{ out[other].println("Echo (" + counter + "): " + str[other]);
if (str[other].trim().equals("BYE"))
done = true;
}
}
incoming.close();
}
catch (Exception e)
{ System.out.println(e);
}
}
}