UDP通信

UDPServer.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.StringReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UDPServer{
	public static void main(String[] args) throws IOException{
		new UDPServerThread().start();
	}
}
class UDPServerThread extends Thread{
	protected DatagramSocket socket=null;
	protected BufferedReader in =null;
	protected Boolean moreQuotes = true;
	public UDPServerThread() throws IOException{
		super();
		socket = new DatagramSocket(4445);
		in = new BufferedReader(new StringReader("one
two
three"));
	}
	public void run(){
		while(moreQuotes){
			try{
				byte[] buf=new byte[256];
				DatagramPacket packet=new DatagramPacket(buf,buf.length);
				socket.receive(packet);
				
				String received =new String(packet.getData(),0,packet.getLength(),"utf-8");
				System.out.println("Server received: "+received);									
				
				String dString = getNextQuote();
				
				buf=dString.getBytes("utf-8");
				
				InetAddress address =packet.getAddress();
				int port =packet.getPort();
				packet = new DatagramPacket(buf,buf.length,address,port);
				socket.send(packet);
			}catch(IOException e){
				e.printStackTrace();
				moreQuotes = false;
			}
		}
		socket.close();
	}
	protected String getNextQuote(){
		String returnValue=null;
		try{
			if((returnValue=in.readLine())==null){
				in.close();
				moreQuotes=false;
				returnValue="No more quotes.Goodbye.";
			}
		}catch(IOException e){
			returnValue="IOException occurred.";
		}
		return returnValue;
	}
}

　　

UDPClient.java

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

class UDPClient{
	public UDPClient(){
		
	}
	public static void main(String[] args) throws IOException{
		if(args.length!=1){
			System.out.println("Usage:java UDPClient……");
			return;
		}
		DatagramSocket socket = new DatagramSocket();
		
		byte[] buf =new byte[256];
		buf[0]='O';
		buf[1]='S';
		InetAddress address= InetAddress.getByName(args[0]);
		DatagramPacket packet =new DatagramPacket(buf,buf.length,address,4445);
		socket.send(packet);
		String send =new String(packet.getData(),0,packet.getLength(),"utf-8");
		System.out.println("Client send: "+send);

		
		packet =new DatagramPacket(buf,buf.length);
		socket.receive(packet);
		
		String received =new String(packet.getData(),0,packet.getLength(),"utf-8");
		System.out.println("Server Say: "+received);
		
		socket.close();
	}
}

　输出：