java - 停止并等待 UDP 服务器

Question

我正在尝试编写一个 Java 停止等待 UDP 服务器，我已经完成了该服务器的工作，但我不确定下一步该去哪里。我希望客户端向服务器发送一条消息，设置超时，等待响应，如果没有得到响应，则重新发送数据包，如果得到响应，则增加序列号。直到达到十并继续与服务器发送和接收消息。

我已经走到这一步了，我该如何解决这个问题？ :

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

public class Client {
  public static void main(String args[]) throws Exception {

    byte[] sendData = new byte[1024];
    byte[] receiveData = new byte[1024];
    InetAddress IPAddress = null;

    try {
      IPAddress = InetAddress.getByName("localhost");
    } catch (UnknownHostException exception) {
      System.err.println(exception);
    }

    //Create a datagram socket object
    DatagramSocket clientSocket = new DatagramSocket();
    while(true) {
      String sequenceNo = "0";
      sendData = sequenceNo.getBytes();
      DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 6789);
      clientSocket.send(sendPacket);
      clientSocket.setSoTimeout(1);
      DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
      if(clientSocket.receive(receivePacket)==null)
      {
       clientSocet.send(sendPacket); 
      }else { //message sent and acknowledgement received
             sequenceNo++; //increment sequence no.
        //Create a new datagram packet to get the response
      String modifiedSentence = sequenceNo;
      //Print the data on the screen
      System.out.println("From :  " + modifiedSentence);
      //Close the socket
      if(sequenceNo >= 10 ) {
        clientSocket.close();
      }
      }}}}

Answer 1

我看到的第一个问题(除了会停止代码编译的错误变量名之外)是套接字超时:如果套接字超时到期，receive 函数将抛出 您的代码无法处理的 SocketTimeoutException 。 receive does not return a value ，因此结果无法与 null 进行比较。相反，您需要执行以下操作:

try {
    clientSocket.receive(receivePacket);
    sequenceNo++;
    ... // rest of the success path
} catch (SocketTimeoutException ex) {
    clientSocket.send(sendPacket);
}