【Java】网络编程UDP 实现消息发送及聊天

小鱼儿 2023-02-25 14:25 26阅读 0赞

TCP可以实现聊天，UDP也可以实现消息发送及聊天。不同的是，TCP需要有服务端和客户端的连接，但UDP不需要，只需要有发送方和接收方即可。

#### 一、实现消息发送 ####

**发送方：**

package com.kuang.lesson03;
    
    import java.net.DatagramPacket;
    import java.net.DatagramSocket;
    import java.net.InetAddress;
    import java.net.SocketException;
    
    //不需要连接服务器
    public class UdpSenderDemo01 { 
        public static void main(String[] args) throws Exception { 
            //1、建议一个Socket
            DatagramSocket socket = new DatagramSocket();
    
            //2、建立包
            String msg = "你好啊，服务器!";
            InetAddress localhost = InetAddress.getByName("localhost");
            int port = 9090;
    
            //数据、数据的长度起始，要发送给谁
            DatagramPacket packet = new DatagramPacket(msg.getBytes(),0,msg.getBytes().length,localhost,port);
    
            //3、发送包
            socket.send(packet);
    
            //4、关闭流
            socket.close();
        }
    }

**接收方：**

package com.kuang.lesson03;
    
    import java.net.DatagramPacket;
    import java.net.DatagramSocket;
    import java.net.SocketException;
    
    // 不是服务端，但是还是要等待客户端的连接。
    // 也就是说只有存在这个才能获得客户端发来的消息
    public class UdpReceiveDemo01 { 
        public static void main(String[] args) throws Exception { 
            //开放端口
            DatagramSocket socket = new DatagramSocket(9090);
    
            //接收数据包
            byte[] buffer = new byte[1024];
            DatagramPacket packet = new DatagramPacket(buffer,0,buffer.length);
    
            socket.receive(packet);//阻塞接收
    
            System.out.println(packet.getAddress().getHostAddress());
            System.out.println(new String(packet.getData(),0,packet.getLength()));
    
            //关闭连接
            socket.close();
        }
    }

**运行结果：**

1、启动接收方开放端口，可以看到一直在运行，也就是在等待消息发来。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70]  
2、启动发送方，可以看到运行结束，说明消息已发送  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70 1]  
3、查看接收方，收到消息。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70 2]

既然UDP能实现消息发送，那么也可以实现聊天。

#### 二、实现聊天 ####

**发送方：**

package com.kuang.chat;
    
    import java.io.BufferedReader;
    import java.io.InputStreamReader;
    import java.net.DatagramPacket;
    import java.net.DatagramSocket;
    import java.net.InetSocketAddress;
    import java.net.SocketException;
    
    public class UdpSenderDemo01 { 
        public static void main(String[] args) throws Exception { 
            DatagramSocket socket = new DatagramSocket(8888);
    
            //准备数据，控制台读取System.in
            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
            while (true) { 
                String data = reader.readLine();
                byte[] datas = data.getBytes();
                DatagramPacket packet = new DatagramPacket(datas,0,datas.length,new InetSocketAddress("localhost",6666));
    
                socket.send(packet);
                if (data.equals("bye")) { 
                    break;
                }
            }
            socket.close();
        }
    }

**接收方：**

package com.kuang.chat;
    
    import java.net.DatagramPacket;
    import java.net.DatagramSocket;
    import java.net.SocketException;
    
    public class UdpReceiveDemo01 { 
        public static void main(String[] args) throws Exception { 
            DatagramSocket socket = new DatagramSocket(6666);
            while (true) { 
                //准备接收数据
                byte[] container = new byte[1024];
                DatagramPacket packet = new DatagramPacket(container,0,container.length);
                socket.receive(packet);//阻塞式接受包裹
    
                //断开连接 bye
                byte[] data = packet.getData();
                String receiveData = new String(data,0,data.length);
    
                System.out.println(receiveData);
                if (receiveData.equals("bye")) { 
                    break;
                }
            }
            socket.close();
        }
    }

**运行结果：**

1、先启动接收方  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70 3]

2、启动发送方  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70 4]  
3、在发送方控制台输入信息并回车  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70 5]  
4、查看接收方，可以看到信息  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDY2ODg5OA_size_16_color_FFFFFF_t_70 6]

这里只实现了单方面的发送，单方面的接收，要实现双方的聊天  
请看：[【Java】网络编程UDP 实现多线程在线聊天][Java_UDP]

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[Java_UDP]: https://blog.csdn.net/weixin_44668898/article/details/107319623