Java Socket 2

《Java TCP/IP Socket 编程》chapter2

这次使用的是UDP协议。

客户端发送一个字符串，服务器接受后，原封不动的返回，在客户端打印出来

Client：

import java.net.DatagramSocket;import java.net.DatagramPacket;import java.net.InetAddress;import java.io.IOException;import java.io.InterruptedIOException;public class UDPEchoClientTimeout {private static final int TIMEOUT = 3000; // Resend timeout (milliseconds)private static final int MAXTRIES = 5; // Maximum retransmissionspublic static void main(String[] args) throws IOException {if ((args.length < 2) || (args.length > 3)) { // Test for correct # of// argsthrow new IllegalArgumentException("Parameter(s): <Server> <Word> [<Port>]");}InetAddress serverAddress = InetAddress.getByName(args[0]); // Server// address// Convert the argument String to bytes using the default encodingbyte[] bytesToSend = args[1].getBytes();int servPort = (args.length == 3) ? Integer.parseInt(args[2]) : 7;DatagramSocket socket = new DatagramSocket();socket.setSoTimeout(TIMEOUT); // Maximum receive blocking time// (milliseconds)DatagramPacket sendPacket = new DatagramPacket(bytesToSend, // Sending// packetbytesToSend.length, serverAddress, servPort);DatagramPacket receivePacket = // Receiving packetnew DatagramPacket(new byte[bytesToSend.length], bytesToSend.length);int tries = 0; // Packets may be lost, so we have to keep tryingboolean receivedResponse = false;do {socket.send(sendPacket); // Send the echo stringtry {socket.receive(receivePacket); // Attempt echo reply receptionif (!receivePacket.getAddress().equals(serverAddress)) {// Check// sourcethrow new IOException("Received packet from an unknown source");}receivedResponse = true;} catch (InterruptedIOException e) { // We did not get anythingtries += 1;System.out.println("Timed out, " + (MAXTRIES - tries)+ " more tries...");}} while ((!receivedResponse) && (tries < MAXTRIES));if (receivedResponse) {System.out.println("Received: "+ new String(receivePacket.getData()));} else {System.out.println("No response -- giving up.");}socket.close();}}

Server：

import java.io.IOException;import java.net.DatagramPacket;import java.net.DatagramSocket;public class UDPEchoServer {private static final int ECHOMAX = 255; // Maximum size of echo datagrampublic static void main(String[] args) throws IOException {if (args.length != 1) { // Test for correct argument listthrow new IllegalArgumentException("Parameter(s): <Port>");}int servPort = Integer.parseInt(args[0]);DatagramSocket socket = new DatagramSocket(servPort);DatagramPacket packet = new DatagramPacket(new byte[ECHOMAX], ECHOMAX);while (true) { // Run forever, receiving and echoing datagramssocket.receive(packet); // Receive packet from clientSystem.out.println("Handling client at "+ packet.getAddress().getHostAddress() + " on port "+ packet.getPort());socket.send(packet); // Send the same packet back to clientpacket.setLength(ECHOMAX); // Reset length to avoid shrinking buffer}/* NOT REACHED */}}