JAVA中基于UDP实现多线程通信

服务器端程序，利用DatagramSocket负责监听端口，当客户端发过来消息时，服务器端就会响应，并将消息内容保存到Datagrampacket对象中，并且！每一次while循环必须重新创建DatagramPacket对象用于保存消息数据。并将socket，packet对象发送给子线程，由子线程完成后面的事务，主线程将进行下一次循环，在receive（packet）处阻塞监听客户端的响应。

package UDPSocketTell;

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

public class UDPServerThreadText {

public static void main(String[] args) throws IOException {
    // TODO Auto-generated method stub
    DatagramSocket socket = new DatagramSocket(8899);
    byte[] infoBytes = new byte[1024];
    int num = 0;
    System.out.println("服务器端启动了·········");
    while (true) {
        DatagramPacket packet = new DatagramPacket(infoBytes, infoBytes.length);
        socket.receive(packet);
        UdpServerThread thread = new UdpServerThread(packet, socket, infoBytes);
        thread.start();
        System.out.println(thread);
        System.out.println("访问的客户端数量：" + (num++));
    }
}

}
在子线程中，由传过来的socket和packet对象获取到客户端传过来的消息数据、端口号和InetAddress地址，将消息数据进行输出，并对客户端进行响应。


package UDPSocketTell;

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

public class UdpServerThread extends Thread {
private String info = null;
private DatagramSocket socket = null;
private int port = 0;
private InetAddress address = null;

public UdpServerThread(DatagramPacket packet2, DatagramSocket socket2, byte[] infoBytes2) {
    // TODO Auto-generated constructor stub
    socket = socket2;
    info = new String(infoBytes2, 0, packet2.getLength());
    port = packet2.getPort();
    address = packet2.getAddress();
}

@Override
public void run() {
    // TODO Auto-generated method stub
    super.run();
    System.out.println("客户端说：" + info);
    byte[] infoBytes = "你好！我是服务器~".getBytes();
    DatagramPacket packet = new DatagramPacket(infoBytes, infoBytes.length, address, port);
    try {
        socket.send(packet);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

}

客户端代码，只需要用DatagramPacket packet = new DatagramPacket(infoBytes, infoBytes.length, address, 8899);保存要发送的数据，指出要发送的目标服务器的地址InetAddress，并用socket.send(packet);发出消息即可。新建一个packet对象，使用socket.receive(packet2);接收服务器的响应。

package UDPSocketTell;

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

/**
* 客户端，基于UDP实现Socket通信
*
* @author 杰仔
*
*/
public class UDPclient {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    byte[] infoBytes = "用户名2：吴俊杰；密码2：123456".getBytes();// 创建发送数据的字节数组
    InetAddress address;
    try {
        /*
         * 发送数据包
         */
        address = InetAddress.getByName("127.0.0.1");
        DatagramPacket packet = new DatagramPacket(infoBytes, infoBytes.length, address, 8899);
        DatagramSocket socket = new DatagramSocket();
        System.out.println("客户端准备发送数据了！");
        socket.send(packet);
        /*
         * 接收数据包响应
         */
        byte[] Bytes = new byte[1024];
        DatagramPacket packet2 = new DatagramPacket(Bytes, Bytes.length);
        System.out.println("**********客户端已经启动************");
        socket.receive(packet2);
        String info = new String(Bytes, 0, packet2.getLength());
        System.out.println("自己的packeg的端口号：" + packet.getPort());
        System.out.println("客户端发来消息长度为 " + packet2.getLength() + " 的消息：" + info + "  消息端口号为：" + packet2.getPort());
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

}

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