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import java.net.*;
import java.io.*;

/** A multithreaded variation of EchoServer.
 *
 *  Taken from Core Web Programming from
 *  Prentice Hall and Sun Microsystems Press,
 *  .
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted.
 */

public class ThreadedEchoServer extends EchoServer
                                implements Runnable {
  public static void main(String[] args) {
    int port = 8088;
    if (args.length > 0) {
      try {
        port = Integer.parseInt(args[0]);
      } catch(NumberFormatException nfe) {}
    }
    ThreadedEchoServer echoServer =
      new ThreadedEchoServer(port, 0);
    echoServer.serverName = "Threaded EchoServer";
  }

  public ThreadedEchoServer(int port, int connections) {
    super(port, connections);
  }

  /** The new version of handleConnection starts a thread. This
   *  new thread will call back to the old version of
   *  handleConnection, resulting in the same server behavior
   *  in a multithreaded version. The thread stores the Socket
   *  instance since run doesn't take any arguments, and since
   *  storing the socket in an instance variable risks having
   *  it overwritten if the next thread starts before the run
   *  method gets a chance to copy the socket reference.
   */

  public void handleConnection(Socket server) {
    Connection connectionThread = new Connection(this, server);
    connectionThread.start();
  }

  public void run() {
    Connection currentThread =
      (Connection)Thread.currentThread();
    try {
      super.handleConnection(currentThread.getSocket());
    } catch(IOException ioe) {
      System.out.println("IOException: " + ioe);
      ioe.printStackTrace();
    }
  }
}

/** This is just a Thread with a field to store a Socket object.
 *  Used as a thread-safe means to pass the Socket from
 *  handleConnection to run.
 */

class Connection extends Thread {
  private Socket serverSocket;

  public Connection(Runnable serverObject,
                    Socket serverSocket) {
    super(serverObject);
    this.serverSocket = serverSocket;
  }

  public Socket getSocket() {
    return serverSocket;
  }
}



EchoServer.java  Creates a Web page showing all data sent from the client (browser). 


import java.net.*;
import java.io.*;
import java.util.StringTokenizer;

/** A simple HTTP server that generates a Web page showing all
 *  of the data that it received from the Web client (usually
 *  a browser). To use this server, start it on the system of
 *  your choice, supplying a port number if you want something
 *  other than port 8088. Call this system server.com. Next,
 *  start a Web browser on the same or a different system, and
 *  connect to http://server.com:8088/whatever. The resultant
 *  Web page will show the data that your browser sent. For 
 *  debugging in servlet or CGI programming, specify 
 *  http://server.com:8088/whatever as the ACTION of your HTML
 *  form. You can send GET or POST data; either way, the
 *  resultant page will show what your browser sent.
 *
 *  Taken from Core Web Programming from 
 *  Prentice Hall and Sun Microsystems Press,
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted. 
 */

public class EchoServer extends NetworkServer {
  protected int maxRequestLines = 50;
  protected String serverName = "EchoServer";

  /** Supply a port number as a command-line
   *  argument. Otherwise, use port 8088.
   */
  
  public static void main(String[] args) {
    int port = 8088;
    if (args.length > 0) {
      try {
        port = Integer.parseInt(args[0]);
      } catch(NumberFormatException nfe) {}
    }
    new EchoServer(port, 0);
  }

  public EchoServer(int port, int maxConnections) {
    super(port, maxConnections);
    listen();
  }

  /** Overrides the NetworkServer handleConnection method to 
   *  read each line of data received, save it into an array
   *  of strings, then send it back embedded inside a PRE 
   *  element in an HTML page.
   */
  
  public void handleConnection(Socket server)
      throws IOException{
    System.out.println
        (serverName + ": got connection from " +
         server.getInetAddress().getHostName());
    BufferedReader in = SocketUtil.getReader(server);
    PrintWriter out = SocketUtil.getWriter(server);
    String[] inputLines = new String[maxRequestLines];
    int i;
    for (i=0; i\n" +
       "\n" +
       "\n" +
       "  \n" +
       "\n" +
       "\n" +
       "\n" +
       "
" + serverName +
         " Results
\n" +
       "Here is the request line and request headers\n" +
       "sent by your browser:\n" +
       "

");
  }

  // Print bottom of a standard Web page.
  
  private void printTrailer(PrintWriter out) {
    out.println
      ("

\n" +
       "\n" +
       "\n");
  }

  // Normal Web page requests use GET, so this server can simply
  // read a line at a time. However, HTML forms can also use 
  // POST, in which case we have to determine the number of POST
  // bytes that are sent so we know how much extra data to read
  // after the standard HTTP headers.
  
  private boolean usingPost(String[] inputs) {
    return(inputs[0].toUpperCase().startsWith("POST"));
  }

  private void readPostData(String[] inputs, int i,
                            BufferedReader in)
      throws IOException {
    int contentLength = contentLength(inputs);
    char[] postData = new char[contentLength];
    in.read(postData, 0, contentLength);
    inputs[++i] = new String(postData, 0, contentLength);
  }

  // Given a line that starts with Content-Length,
  // this returns the integer value specified.
  
  private int contentLength(String[] inputs) {
    String input;
    for (int i=0; iOverride this method in servers
   *  you write.
   *  


   *  This generic version simply reports the host that made
   *  the connection, shows the first line the client sent,
   *  and sends a single line in response.
   */

  protected void handleConnection(Socket server)
      throws IOException{
    BufferedReader in = SocketUtil.getReader(server);
    PrintWriter out = SocketUtil.getWriter(server);
    System.out.println
      ("Generic Network Server: got connection from " +
       server.getInetAddress().getHostName() + "\n" +
       "with first line '" + in.readLine() + "'");
    out.println("Generic Network Server");
    server.close();
  }

  /** Gets the max connections server will handle before
   *  exiting. A value of 0 indicates that server should run
   *  until explicitly killed.
   */

  public int getMaxConnections() {
    return(maxConnections);
  }

  /** Sets max connections. A value of 0 indicates that server
   *  should run indefinitely (until explicitly killed).
   */

  public void setMaxConnections(int maxConnections) {
    this.maxConnections = maxConnections;
  }

  /** Gets port on which server is listening. */

  public int getPort() {
    return(port);
  }

  /** Sets port. You can only do before "connect" is
   *  called. That usually happens in the constructor.
   */

  protected void setPort(int port) {
    this.port = port;
  }
}


SocketUtil.java  Simplifies the creation of a PrintWriter and BufferedReader.

import java.net.*;
import java.io.*;

/** A shorthand way to create BufferedReaders and
 *  PrintWriters associated with a Socket.
 *
 *  Taken from Core Web Programming from 
 *  Prentice Hall and Sun Microsystems Press,
 *  © 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted. 
 */

public class SocketUtil {
  /** Make a BufferedReader to get incoming data. */

  public static BufferedReader getReader(Socket s)
      throws IOException {
    return(new BufferedReader(
       new InputStreamReader(s.getInputStream())));
  }

  /** Make a PrintWriter to send outgoing data.
   *  This PrintWriter will automatically flush stream
   *  when println is called.
   */

  public static PrintWriter getWriter(Socket s)
      throws IOException {
    // Second argument of true means autoflush.
    return(new PrintWriter(s.getOutputStream(), true));
  }
}