UDP网络编程

UDP网络编程

UDP不需要连接服务器。

只需要指定发送的目标IP和端口号即可。

对于发送数据的一端：

建socket只用填自己的端口号，发送数据包才填对方的ip和端口。

//1、需要指定自己的socket的端口号，但socket不用指定对方的端口和ip
DatagramSocket socket = new DatagramSocket(9998);
//2、获取发送的消息
String msg = new Scanner(System.in).nextLine();
int port = 9999; // 指定目标端口号
InetAddress inetAddress = InetAddress.getByName("localhost"); //指定目标主机IP
//3、封装成数据报，在数据包才指定发送的对方的ip和端口号
DatagramPacket packet = new DatagramPacket(msg.getBytes(),0,
    msg.getBytes().length,inetAddress,port);//注意这里的长度是字节流的长度，不是字符串的长度！！！
//3、发送数据包
socket.send(packet);

对于接收数据的一端：

建socket只用填自己的端口号，然后建个缓存封装成数据包，等待接收即可。

//1、需要指定自己的socket的端口号，但socket不用指定对方的端口和ip
DatagramSocket socket = new DatagramSocket(9999);
//2、接收数据包,接收数据包需要缓存，再用数据包类型封装缓存
byte[] buffer = new byte[1024];
DatagramPacket packet = new DatagramPacket(buffer,0,buffer.length);
socket.receive(packet); //阻塞性接收，即收不到就一直等待
//3、输出查看
String ip = packet.getAddress().getHostAddress();
String msg = new String(packet.getData(),0,packet.getLength()); //这里必须新new一个String并且指定packet.getLength()长度，利用构造函数转换
System.out.println("收到数据，来自"+ip+"，内容为："+msg);

多线程 聊天系统

TalkSend

package com.net.transudp.udpmutichat;

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

/**
 * 执行发送数据包功能的线程,需要指定本地端口，和对方端口和对方IP
 */
public class TalkSend implements Runnable{
  DatagramSocket socket = null;
  BufferedReader reader = null;

  private int fromPort;
  private String toIp;
  private int toPort;

  public TalkSend(int fromPort, String toIp, int toPort) {
    this.fromPort = fromPort;
    this.toIp = toIp;
    this.toPort = toPort;
    try {
      this.socket = new DatagramSocket(fromPort); //指定自己的端口号
      reader = new BufferedReader(new InputStreamReader(System.in));
    } catch (SocketException e) {
      throw new RuntimeException(e);
    }
  }

  @Override
  public void run() {
    String msg = "";
    while(true){
      try {
        msg = reader.readLine();
        byte[] msgs = msg.getBytes();
        //3、建包发送,必须指定对方的ip和端口
        DatagramPacket packet = new DatagramPacket(msgs,0,msgs.length,new InetSocketAddress(toIp,toPort));
        socket.send(packet);
        if(msg.equals("bye")){
          break;
        }
      } catch (IOException e) {
        throw new RuntimeException(e);
      }
    }
    socket.close();

  }
}

TalkReceive

package com.net.transudp.udpmutichat;

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

/**
 * 执行接收数据包的线程，需要指定本地端口号
 */
public class TalkReceive implements Runnable{
  DatagramSocket socket = null;
  private int port;

  public TalkReceive(int port) {
    this.port = port;
    try {
      this.socket = new DatagramSocket(port); //指定接收的端口号
    } catch (SocketException e) {
      throw new RuntimeException(e);
    }
  }

  @Override
  public void run() {
    while(true){
      try {
        //准备接收
        byte[] buffer = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer,0,buffer.length);
        socket.receive(packet); //阻塞接收
        byte[] data = packet.getData(); //返回的数据是字节流
        String msg = new String(data,0,packet.getLength()); //需指定包裹长度
        System.out.println("来自端口"+packet.getPort()+": "+msg);
        if(msg.equals("bye")){
          break;
        }
      } catch (IOException e) {
        throw new RuntimeException(e);
      }
    }
    socket.close();

  }
}

聊天用户

package com.net.transudp.udpmutichat;

public class TalkMan1 {

  public static void main(String[] args) {
    //开启两个线程
    new Thread(new TalkSend(7777,"localhost",9999)).start();
    new Thread(new TalkReceive(8888)).start();
  }
}

package com.net.transudp.udpmutichat;

public class TalkMan2 {

  public static void main(String[] args) {
    //开启两个线程
    new Thread(new TalkSend(7778,"localhost",8888)).start();
    new Thread(new TalkReceive(9999)).start();
  }

}