programming-examples/java/Basics/TimeServer.java

TimeServer



import java.io.*;
import java.net.*;
import java.nio.*;
import java.nio.channels.*;
import java.nio.charset.*;
import java.util.*;
import java.util.regex.*;


public class TimeServer {

    // We can't use the normal daytime port (unless we're running as root,
    // which is unlikely), so we use this one instead
    private static int PORT = 8013;

    // The port we'll actually use
    private static int port = PORT;

    // Charset and encoder for US-ASCII
    private static Charset charset = Charset.forName("US-ASCII");
    private static CharsetEncoder encoder = charset.newEncoder();

    // Direct byte buffer for writing
    private static ByteBuffer dbuf = ByteBuffer.allocateDirect(1024);


    // Open and bind the server-socket channel
    //
    private static ServerSocketChannel setup() throws IOException {
    ServerSocketChannel ssc = ServerSocketChannel.open();
    InetSocketAddress isa
        = new InetSocketAddress(InetAddress.getLocalHost(), port);
    ssc.socket().bind(isa);
    return ssc;
    }

    // Service the next request to come in on the given channel
    //
    private static void serve(ServerSocketChannel ssc) throws IOException {
    SocketChannel sc = ssc.accept();
    try {
        String now = new Date().toString();
        sc.write(encoder.encode(CharBuffer.wrap(now + "
")));
        System.out.println(sc.socket().getInetAddress() + " : " + now);
        sc.close();
    } finally {
        // Make sure we close the channel (and hence the socket)
        sc.close();
    }
    }

    public static void main(String[] args) throws IOException {
    if (args.length > 1) {
        System.err.println("Usage: java TimeServer [port]");
        return;
    }

    // If the first argument is a string of digits then we take that
    // to be the port number
    if ((args.length == 1) && Pattern.matches("[0-9]+", args[0]))
        port = Integer.parseInt(args[0]);

    ServerSocketChannel ssc = setup();
    for (;;)
        serve(ssc);

    }

}