/* * Copyright (c) 2000 David Flanagan.  All rights reserved. * This code is from the book Java Examples in a Nutshell, 2nd 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. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book (recommended), * visit http://www.davidflanagan.com/javaexamples2. */package com.davidflanagan.examples.net;import java.io.*;import java.net.*;/** * This program connects to a server at a specified host and port. * It reads text from the console and sends it to the server. * It reads text from the server and sends it to the console. **/public class GenericClient {    public static void main(String[] args) throws IOException {        try {            // Check the number of arguments            if (args.length != 2)                 throw new IllegalArgumentException("Wrong number of args");	                // Parse the host and port specifications            String host = args[0];            int port = Integer.parseInt(args[1]);                        // Connect to the specified host and port            Socket s = new Socket(host, port);	                // Set up streams for reading from and writing to the server.            // The from_server stream is final for use in the inner class below            final Reader from_server=new InputStreamReader(s.getInputStream());            PrintWriter to_server = new PrintWriter(s.getOutputStream());                        // Set up streams for reading from and writing to the console            // The to_user stream is final for use in the anonymous class below            BufferedReader from_user =                 new BufferedReader(new InputStreamReader(System.in));	    // Pass true for auto-flush on println()	    final PrintWriter to_user = new PrintWriter(System.out, true);                        // Tell the user that we've connected            to_user.println("Connected to " + s.getInetAddress() +			    ":" + s.getPort());                        // Create a thread that gets output from the server and displays             // it to the user.  We use a separate thread for this so that we            // can receive asynchronous output            Thread t = new Thread() {                public void run() {                    char[] buffer = new char[1024];                    int chars_read;                    try { 			// Read characters until the stream closes                        while((chars_read = from_server.read(buffer)) != -1) {			    // Loop through the array of characters, and 			    // print them out, converting all \n characters			    // to the local platform's line terminator.			    // This could be more efficient, but it is probably			    // faster than the network is, which is good enough			    for(int i = 0; i < chars_read; i++) {				if (buffer[i] == '\n') to_user.println();				else to_user.print(buffer[i]);			    }			    to_user.flush();			}                    }                    catch (IOException e) { to_user.println(e); }                    // When the server closes the connection, the loop above                    // will end.  Tell the user what happened, and call                    // System.exit(), causing the main thread to exit along                    // with this one.		    to_user.println("Connection closed by server.");                    System.exit(0);                }            };                        // We set the priority of the server-to-user thread above to be            // one level higher than the main thread.  We shouldn't have to do            // this, but on some operating systems, output sent to the console            // doesn't appear when a thread at the same priority level is            // blocked waiting for input from the console.            t.setPriority(Thread.currentThread().getPriority() + 1);                        // Now start the server-to-user thread            t.start();                        // In parallel, read the user's input and pass it on to the server.            String line;            while((line = from_user.readLine()) != null) {                to_server.print(line + "\n");                to_server.flush();            }                        // If the user types a Ctrl-D (Unix) or Ctrl-Z (Windows) to end            // their input, we'll get an EOF, and the loop above will exit.            // When this happens, we stop the server-to-user thread and close            // the socket.            s.close();            to_user.println("Connection closed by client.");	    System.exit(0);        }        // If anything goes wrong, print an error message        catch (Exception e) {             System.err.println(e);            System.err.println("Usage: java GenericClient <hostname> <port>");        }    }}