Java/Network Protocol/ServerSocketChannel

A simple TCP server for the daytime service

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/*

* Copyright (c) 2004 David Flanagan.  All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book, 
* please visit http://www.davidflanagan.ru/javaexamples3.
*/

//package je3.nio; import java.net.InetSocketAddress; import java.nio.ByteBuffer; import java.nio.CharBuffer; import java.nio.channels.ServerSocketChannel; import java.nio.channels.SocketChannel; import java.nio.charset.Charset; import java.nio.charset.CharsetEncoder; /**

* A simple TCP server for the daytime service. See RFC867 for details. This
* implementation lacks meaningful exception handling and cannot handle UDP
* connections.
*/

public class SimpleDaytimeServer {

 public static void main(String args[]) throws java.io.IOException {
   // RFC867 specifies port 13 for this service. On Unix platforms,
   // you need to be running as root to use that port, so we allow
   // this service to use other ports for testing.
   int port = 13;
   if (args.length > 0)
     port = Integer.parseInt(args[0]);
   // Create a channel to listen for connections on.
   ServerSocketChannel server = ServerSocketChannel.open();
   // Bind the channel to a local port. Note that we do this by obtaining
   // the underlying java.net.ServerSocket and binding that socket.
   server.socket().bind(new InetSocketAddress(port));
   // Get an encoder for converting strings to bytes
   CharsetEncoder encoder = Charset.forName("US-ASCII").newEncoder();
   for (;;) { // Loop forever, processing client connections
     // Wait for a client to connect
     SocketChannel client = server.accept();
     // Build response string, wrap, and encode to bytes
     String date = new java.util.Date().toString() + "\r\n";
     ByteBuffer response = encoder.encode(CharBuffer.wrap(date));
     // Send the response to the client and disconnect.
     client.write(response);
     client.close();
   }
 }

}

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