useudpechoserver.java

JAVA实现的使用UDP实现Echo服务

import java.net.*;
import java.io.*;

public class useUDPEchoServer extends Thread 
{
	//设置常量
  	public final static int defaultport = 7;
  	//设置属性
  	private int bufferSize; 
  	protected DatagramSocket ds;
	//构造器
  	public useUDPEchoServer(int port, int bufferSize) 
  	throws SocketException 
  	{
  		this.bufferSize = bufferSize;
    		this.ds = new DatagramSocket(port);    
  	}
  	
  	public useUDPEchoServer(int port) 
  	throws SocketException 
  	{
  		this(port, 8192);
  		ds.setReceiveBufferSize(32768);  		   
  	}
  	
  	public useUDPEchoServer() 
  	throws SocketException 
  	{
  		this(defaultport);  		  		   
  	}
  	
  	//线程运行
  	public void run() 
  	{
  		//缓存  
    		byte[] buffer = new byte[bufferSize];
    		//无限循环
    		while (true) 
    		{
    			//带寻址信息的数据包
      			DatagramPacket incoming = new DatagramPacket(buffer, buffer.length);
      			try 
      			{
      				//接收数据信息
        			ds.receive(incoming);
        			//响应
        			this.respond(incoming);
      			}
      			//捕获异常
      			catch (IOException e) 
      			{
        			System.err.println(e);
      			}      
    		} // end while
  	}  // end run  
  	
	//响应
  	public void respond(DatagramPacket incoming) 
  	{
    		try 
    		{
      			DatagramPacket outgoing = new DatagramPacket(incoming.getData(), 
       			incoming.getLength(), incoming.getAddress(), incoming.getPort());
       			//发送数据包
      			ds.send(outgoing);
      			//显示数据包信息长度
      			System.out.println(incoming.getLength());
    		}
    		catch (IOException e) 
    		{
      			System.err.println(e);
    		}    
  	}

  	public static void main(String[] args) 
  	{ 
   		try 
   		{
     			if (args.length > 0) 
     			{
       				int port = Integer.parseInt(args[0]);
       				useUDPEchoServer server = new useUDPEchoServer(port);
       				//启动服务
       				server.start();       
     			}
     			else 
     			{
     				//使用缺省端口
       				useUDPEchoServer server = new useUDPEchoServer();
       				server.start();
     			}
   		}
   		//捕获异常
   		catch (SocketException e) 
   		{
     			System.err.println(e);
   		} 
  	}
}