java - Java UDP连接

我正在使用Netbeans IDE尝试在客户端和服务器之间建立UDP连接，这是一个简单的程序， UDPClient 将字符串发送到 UDPServer ，服务器将字符串大写并将其发送回客户端。端和服务器端在一个分开的项目中。

我的客户端UDPClient的类代码:

    package udpclient;


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

    public class UDPClient {

        public static void main(String[] args) throws IOException{

            //get input from user
            BufferedReader user_in = new BufferedReader(
                    new InputStreamReader(System.in));

            //create udp socket connection
            DatagramSocket socket = new DatagramSocket();

            //creat buffers to process data
            byte[] inData = new byte[1024];
            byte[] outData = new byte[1024];

            //get ip destination wanted
            InetAddress IP = InetAddress.getByName("localhost");

            //read data from user
            System.out.println("Enter Data to send to server: ");
            outData = user_in.readLine().getBytes();


            /*
             * make pkts for interaction
             */
            //send pkts
            DatagramPacket sendPkt = new DatagramPacket(outData, outData.length, IP, 9876);
            socket.send(sendPkt);

            //receive pkts
            DatagramPacket recievePkt = new DatagramPacket(inData, inData.length);
            socket.receive(recievePkt);

            System.out.println("Replay from Server: "+recievePkt.getData());

        }
    }

和我的服务器端类UDPServer:

    package udpserver;

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

    public class UDPServer {


        public static void main(String[] args) throws IOException{
            // TODO code application logic
            //connection
            DatagramSocket socket = new DatagramSocket();

            //pkt buffers
            byte[] inServer = new byte[1024];
            byte[] outServer = new byte[1024];

            //receive pkt
            DatagramPacket rcvPkt = new DatagramPacket(inServer,inServer.length);
            socket.receive(rcvPkt);
            //display receive
            System.out.println("Packet Received!");


            //retrive pkt info to send response to same sender
            InetAddress IP = rcvPkt.getAddress();
            int port = rcvPkt.getPort();

            //process data
            String temp = new String(rcvPkt.getData());
            temp = temp.toUpperCase();
            outServer = temp.getBytes();

            //send response packet to sender
            DatagramPacket sndPkt = new DatagramPacket(outServer, outServer.length, IP, port);
            socket.send(sndPkt);

        }
    }

计算程序正常运行并且不输出错误。服务器根本没有收到数据包，也没有与客户端进行交互。为什么会这样呢？

最佳答案

您尚未在服务器中指定任何侦听端口，因此服务器在随机可用端口上侦听。

在服务器端尝试

DatagramSocket socket = new DatagramSocket(9876);