Java-UDP通讯（双向）

新建两个工程，一个Send,一个Receive，先启动Receive,再启动Send，至此就可以双向通信

Send工程：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;

public class Send {
	//接收消息的端口
	private static final int PORT_RECEIVE = 8080;

	public static void main(String[] args) {
		handler();
	}

	private static void handler() {
		DatagramSocket sendSocket = null;
		DatagramSocket receiveSocket = null;
		try {
			//实例化两个套接字，一个用于接收消息，一个用于发送消息
			sendSocket = new DatagramSocket();
			receiveSocket = new DatagramSocket(PORT_RECEIVE);

			//实例化线程并启动，一个用于接收消息，一个用于发送消息
			new Thread(new SendThread(sendSocket)).start();
			new Thread(new ReceiveThread(receiveSocket)).start();
		} catch (SocketException e) {
			System.out.println("handler:异常！");
		}
	}
}

/*
 * 发送消息的线程类
 */
class SendThread implements Runnable{
	//将消息发送到指定端口和地址
	private static final int PORT_SEND = 9090;
	private static final String IP_SEND = "localhost";
	private DatagramSocket sendSocket;

	public SendThread(DatagramSocket sendSocket) {
		this.sendSocket = sendSocket;
	}

	@Override
	public void run() {
		BufferedReader br = null;
		try {
			while(true){
				//键盘录入
				br = new BufferedReader(new InputStreamReader(System.in));
				String line = null;
				while((line = br.readLine()) != null){
					//将键盘录入的内容转换成字节数组
					byte[] buf = line.getBytes();
					//实例化一个数据包，指定发送的内容，内容长度，发送的地址和端口
					DatagramPacket dp = new DatagramPacket(buf, buf.length, InetAddress.getByName(IP_SEND), PORT_SEND);
					//发送数据包
					sendSocket.send(dp);
					//打印发送的内容
					System.out.println("I:" + line);
				}
			}
		} catch (IOException e) {
			System.out.println("send fail！");
		}finally{
			if(sendSocket != null){
				sendSocket.close();
			}
			if(br != null){
				try {
					br.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
}

/*
 * 接收消息的线程类
 */
class ReceiveThread implements Runnable{
	private DatagramSocket receiveSocket;

	public ReceiveThread(DatagramSocket receiveSocket) {
		this.receiveSocket = receiveSocket;
	}

	@Override
	public void run() {
		try {
			while(true){
				//一次接收的内容的最大容量
				byte[] buf = new byte[1024];
				DatagramPacket dp = new DatagramPacket(buf, buf.length);
				//接收数据包
				receiveSocket.receive(dp);
				//取得数据包里的内容 
				String data = new String(dp.getData(), 0, dp.getLength());
				//打印接收到的数据
				System.out.println("Other:" + data);
			}
		} catch (IOException e) {
			System.out.println("receive fail");
		}finally{
			if(receiveSocket != null){
				receiveSocket.close();
			}
		}
	}
}

Receive工程：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;

public class Receive {
	//接收消息的端口
	private static final int PORT_RECEIVE = 9090;

	public static void main(String[] args) {
		handler();
	}

	private static void handler() {
		DatagramSocket sendSocket = null;
		DatagramSocket receiveSocket = null;
		try {
			//实例化两个套接字，一个用于接收消息，一个用于发送消息
			sendSocket = new DatagramSocket();
			receiveSocket = new DatagramSocket(PORT_RECEIVE);
			//实例化线程并启动，一个用于接收消息，一个用于发送消息
			new Thread(new SendThread(sendSocket)).start();
			new Thread(new ReceiveThread(receiveSocket)).start();
		} catch (SocketException e) {
			System.out.println("handler:异常！");
		}
	}
}

/*
 * 发送消息的线程类
 */
class SendThread implements Runnable{
	//将消息发送到指定端口和地址
	private static final int PORT_SEND = 8080;
	private static final String IP_SEND = "localhost";
	private DatagramSocket sendSocket;

	public SendThread(DatagramSocket sendSocket) {
		this.sendSocket = sendSocket;
	}

	@Override
	public void run() {
		BufferedReader br = null;
		try {
			while(true){
				//键盘录入
				br = new BufferedReader(new InputStreamReader(System.in));
				String line = null;
				while((line = br.readLine()) != null){
					//将键盘录入的内容转换成字节数组
					byte[] buf = line.getBytes();
					//实例化一个数据包，指定发送的内容，内容长度，发送的地址和端口
					DatagramPacket dp = new DatagramPacket(buf, buf.length, InetAddress.getByName(IP_SEND), PORT_SEND);
					//发送数据包
					sendSocket.send(dp);
					//打印发送的内容
					System.out.println("I:" + line);
				}
			}
		} catch (IOException e) {
			System.out.println("send fail");
		}finally{
			if(sendSocket != null){
				sendSocket.close();
			}
			if(br != null){
				try {
					br.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
}

/*
 * 接收消息的线程类
 */
class ReceiveThread implements Runnable{
	private DatagramSocket receiveSocket;

	public ReceiveThread(DatagramSocket receiveSocket) {
		this.receiveSocket = receiveSocket;
	}

	@Override
	public void run() {
		try {
			while(true){
				//一次接收的内容的最大容量
				byte[] buf = new byte[1024];
				DatagramPacket dp = new DatagramPacket(buf, buf.length);
				//接收数据包
				receiveSocket.receive(dp);
				String data = new String(dp.getData(), 0, dp.getLength());
				//取得数据包里的内容 
				System.out.println("Other:" + data);
			}
		} catch (IOException e) {
			System.out.println("receive fail");
		}finally{
			if(receiveSocket != null){
				receiveSocket.close();
			}
		}
	}
}