Java example source code file (NetworkServer.java)

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Java - Java tags/keywords

cloneable, clonenotsupportedexception, echo, internalerror, ioexception, iso8859_1, net, network, networkserver, object, printstream, runnable, server, serversocket, socket, thread

The NetworkServer.java Java example source code

/*
 * Copyright (c) 1995, 2011, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package sun.net;

import java.io.*;
import java.net.Socket;
import java.net.ServerSocket;

/**
 * This is the base class for network servers.  To define a new type
 * of server define a new subclass of NetworkServer with a serviceRequest
 * method that services one request.  Start the server by executing:
 * <pre>
 *      new MyServerClass().startServer(port);
 * </pre>
 */
public class NetworkServer implements Runnable, Cloneable {
    /** Socket for communicating with client. */
    public Socket clientSocket = null;
    private Thread serverInstance;
    private ServerSocket serverSocket;

    /** Stream for printing to the client. */
    public PrintStream clientOutput;

    /** Buffered stream for reading replies from client. */
    public InputStream clientInput;

    /** Close an open connection to the client. */
    public void close() throws IOException {
        clientSocket.close();
        clientSocket = null;
        clientInput = null;
        clientOutput = null;
    }

    /** Return client connection status */
    public boolean clientIsOpen() {
        return clientSocket != null;
    }

    final public void run() {
        if (serverSocket != null) {
            Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
            // System.out.print("Server starts " + serverSocket + "\n");
            while (true) {
                try {
                    Socket ns = serverSocket.accept();
//                  System.out.print("New connection " + ns + "\n");
                    NetworkServer n = (NetworkServer)clone();
                    n.serverSocket = null;
                    n.clientSocket = ns;
                    new Thread(n).start();
                } catch(Exception e) {
                    System.out.print("Server failure\n");
                    e.printStackTrace();
                    try {
                        serverSocket.close();
                    } catch(IOException e2) {}
                    System.out.print("cs="+serverSocket+"\n");
                    break;
                }
            }
//          close();
        } else {
            try {
                clientOutput = new PrintStream(
                        new BufferedOutputStream(clientSocket.getOutputStream()),
                                               false, "ISO8859_1");
                clientInput = new BufferedInputStream(clientSocket.getInputStream());
                serviceRequest();
                // System.out.print("Service handler exits
                // "+clientSocket+"\n");
            } catch(Exception e) {
                // System.out.print("Service handler failure\n");
                // e.printStackTrace();
            }
            try {
                close();
            } catch(IOException e2) {}
        }
    }

    /** Start a server on port <i>port.  It will call serviceRequest()
        for each new connection. */
    final public void startServer(int port) throws IOException {
        serverSocket = new ServerSocket(port, 50);
        serverInstance = new Thread(this);
        serverInstance.start();
    }

    /** Service one request.  It is invoked with the clientInput and
        clientOutput streams initialized.  This method handles one client
        connection. When it is done, it can simply exit. The default
        server just echoes it's input. It is invoked in it's own private
        thread. */
    public void serviceRequest() throws IOException {
        byte buf[] = new byte[300];
        int n;
        clientOutput.print("Echo server " + getClass().getName() + "\n");
        clientOutput.flush();
        while ((n = clientInput.read(buf, 0, buf.length)) >= 0) {
            clientOutput.write(buf, 0, n);
        }
    }

    public static void main(String argv[]) {
        try {
            new NetworkServer ().startServer(8888);
        } catch (IOException e) {
            System.out.print("Server failed: "+e+"\n");
        }
    }

    /**
     * Clone this object;
     */
    public Object clone() {
        try {
            return super.clone();
        } catch (CloneNotSupportedException e) {
            // this shouldn't happen, since we are Cloneable
            throw new InternalError(e);
        }
    }

    public NetworkServer () {
    }
}