Network Programming, UDP Echo Client

When network testing, it is useful to have a client program connects to a UDP server and gets an echo of a text string that you send to the server:

 import java.net.*;import java.io.*;import java.util.*;class SocketUdpEcho01{	public static void main(String[] args){		String server = "www.austin.cc.tx.us";		int port = 7; //echo port		String msg = "This is a UDP echo test";		try{    			//Convert the message to a byte array			byte[] udpMsg = msg.getBytes();			InetAddress addr = InetAddress.getByName(server);			//Create a packet			DatagramPacket packet = 				new DatagramPacket(udpMsg,udpMsg.length,addr,port);			//Get a datagram socket to send the message			DatagramSocket datagramSocket = new DatagramSocket();			//Send the message			datagramSocket.send(packet);      			//Overwrite the msg in the packet to confirm that			//an echo is really received			byte[] dataArray = packet.getData();			for(int cnt = 0; cnt < packet.getLength(); cnt++)				dataArray[cnt] = 'x';			//Display overwritten version			System.out.println(new String(packet.getData()));			//Receive the echo into the same packet.			datagramSocket.receive(packet);			//Display the echo			System.out.println(new String(packet.getData()));			datagramSocket.close();		}//end try		catch(UnknownHostException e){			System.out.println(e);			System.out.println(					"Connection Failure. Are you online?");		}//end catch UnknownHostException    		catch(SocketException e){System.out.println(e);}		catch(IOException e){System.out.println(e);}    	}//end main}//end class SocketUdpEcho01

After editing your favorite Web server name into the string named server, the program should display:

 xxxxxxxxxxxxxxxxxxxxxxx

If another message is displayed, you should try another server. This code was tested using JDK 1.1.6 under Win95.

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