EchoServerThreaded2.java

package network;

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

/**
 * Threaded Echo Server, pre-allocation scheme.
 * Each Thread waits in its accept() call for a connection; this synchronizes
 * on the serversocket when calling its accept() method.
 * @author Ian F. Darwin.
 */
// BEGIN main
public class EchoServerThreaded2 {

    public static final int ECHOPORT = 7;

    public static final int NUM_THREADS = 4;

    /** Main method, to start the servers. */
    public static void main(String[] av) {
        new EchoServerThreaded2(ECHOPORT, NUM_THREADS);
    }

    /** Constructor */
    public EchoServerThreaded2(int port, int numThreads) {
        ServerSocket servSock;

        try {
            servSock = new ServerSocket(port);

        } catch(IOException e) {
            /* Crash the server if IO fails. Something bad has happened */
            throw new RuntimeException("Could not create ServerSocket ", e);
        }

        // Create a series of threads and start them.
        for (int i=0; i<numThreads; i++) {
            new Handler(servSock, i).start();
        }
    }

    /** A Thread subclass to handle one client conversation. */
    class Handler extends Thread {
        ServerSocket servSock;
        int threadNumber;

        /** Construct a Handler. */
        Handler(ServerSocket s, int i) {
            servSock = s;
            threadNumber = i;
            setName("Thread " + threadNumber);
        }

        public void run() {
            /* Wait for a connection. Synchronized on the ServerSocket
             * while calling its accept() method.
             */
            while (true) {
                try {
                    System.out.println( getName() + " waiting");

                    Socket clientSocket;
                    // Wait here for the next connection.
                    synchronized(servSock) {
                        clientSocket = servSock.accept();
                    }
                    System.out.println(getName() + " starting, IP=" +
                        clientSocket.getInetAddress());
                    BufferedReader is = new BufferedReader(
                        new InputStreamReader(clientSocket.getInputStream()));
                    PrintStream os = new PrintStream(
                        clientSocket.getOutputStream(), true);
                    String line;
                    while ((line = is.readLine()) != null) {
                        os.print(line + "\r\n");
                        os.flush();
                    }
                    System.out.println(getName() + " ENDED ");
                    clientSocket.close();
                } catch (IOException ex) {
                    System.out.println(getName() + ": IO Error on socket " + ex);
                    return;
                }
            }
        }
    }
}
// END main