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What this is

This file is included in the "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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The source code

 * Copyright 2001-2004 The Apache Software Foundation
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.
package examples;


 * This is an example program demonstrating how to use the EchoTCPClient
 * and EchoUDPClient classes.  This program connects to the default echo
 * service port of a specified server, then reads lines from standard
 * input, writing them to the echo server, and then printing the echo.
 * The default is to use the TCP port.  Use the -udp flag to use the UDP
 * port.

* Usage: echo [-udp] *

***/ public final class echo { public static final void echoTCP(String host) throws IOException { EchoTCPClient client = new EchoTCPClient(); BufferedReader input, echoInput; PrintWriter echoOutput; String line; // We want to timeout if a response takes longer than 60 seconds client.setDefaultTimeout(60000); client.connect(host); System.out.println("Connected to " + host + "."); input = new BufferedReader(new InputStreamReader(; echoOutput = new PrintWriter(new OutputStreamWriter(client.getOutputStream()), true); echoInput = new BufferedReader(new InputStreamReader(client.getInputStream())); while ((line = input.readLine()) != null) { echoOutput.println(line); System.out.println(echoInput.readLine()); } client.disconnect(); } public static final void echoUDP(String host) throws IOException { int length, count; byte[] data; String line; BufferedReader input; InetAddress address; EchoUDPClient client; input = new BufferedReader(new InputStreamReader(; address = InetAddress.getByName(host); client = new EchoUDPClient();; // If we don't receive an echo within 5 seconds, assume the packet is lost. client.setSoTimeout(5000); System.out.println("Ready to echo to " + host + "."); // Remember, there are no guarantees about the ordering of returned // UDP packets, so there is a chance the output may be jumbled. while ((line = input.readLine()) != null) { data = line.getBytes(); client.send(data, address); count = 0; do { try { length = client.receive(data); } // Here we catch both SocketException and InterruptedIOException, // because even though the JDK 1.1 docs claim that // InterruptedIOException is thrown on a timeout, it seems // SocketException is also thrown. catch (SocketException e) { // We timed out and assume the packet is lost. System.err.println( "SocketException: Timed out and dropped packet"); break; } catch (InterruptedIOException e) { // We timed out and assume the packet is lost. System.err.println( "InterruptedIOException: Timed out and dropped packet"); break; } System.out.print(new String(data, 0, length)); count += length; } while (count < data.length); System.out.println(); } client.close(); } public static final void main(String[] args) { if (args.length == 1) { try { echoTCP(args[0]); } catch (IOException e) { e.printStackTrace(); System.exit(1); } } else if (args.length == 2 && args[0].equals("-udp")) { try { echoUDP(args[1]); } catch (IOException e) { e.printStackTrace(); System.exit(1); } } else { System.err.println("Usage: echo [-udp] "); System.exit(1); } } }

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