是啥导致我的基本客户端/服务器套接字程序中的循环在第二次尝试时失败？ [关闭]

Posted 2023-02-18

【中文标题】是啥导致我的基本客户端/服务器套接字程序中的循环在第二次尝试时失败？ [关闭]

【英文标题】：What is causing the loop in my basic client/server socket program to fail on second attempt? [closed]是什么导致我的基本客户端/服务器套接字程序中的循环在第二次尝试时失败？ [关闭]

【发布时间】：2021-11-11 22:05:59

【问题描述】：

我制作了一个基本的套接字程序，用于在同一主机上的服务器和客户端之间发送消息。我可以发送一条消息，但在第二条消息上它退出。问题是它应该只在我输入“Bye”时退出。我知道我的 while 循环有问题，但我不知道为什么。这是我的代码：

客户：

import java.io.*;
import java.net.Socket;
import java.util.Scanner;

public class Client3 

    public static void main(String[] args) 
        Socket socket = null;
        InputStreamReader inputStreamReader = null;
        OutputStreamWriter outputStreamWriter = null;
        BufferedReader bufferedReader = null;
        BufferedWriter bufferedWriter = null;

        try 
            socket = new Socket("localhost", 4321);

            inputStreamReader = new InputStreamReader(socket.getInputStream());
            outputStreamWriter = new OutputStreamWriter(socket.getOutputStream());

            bufferedReader = new BufferedReader(inputStreamReader);
            bufferedWriter = new BufferedWriter(outputStreamWriter);

            Scanner scanner = new Scanner(System.in);
             boolean loopIT;
             loopIT = true;

            while (loopIT) 
                String msgToSend = scanner.nextLine();
                bufferedWriter.write(msgToSend);
                bufferedWriter.newLine();
                bufferedWriter.flush();

                System.out.println("Server:" + bufferedReader.readLine());
                if(msgToSend.equalsIgnoreCase("Bye")) 
                    loopIT = false;
                 else 
                    loopIT = true;
                

            

         catch (IOException e) 
            e.printStackTrace();
         finally 
            try 
                if(socket != null)
                    socket.close();
                if(inputStreamReader != null)
                    inputStreamReader.close();
                if(outputStreamWriter != null)
                    outputStreamWriter.close();
                if (bufferedReader != null)
                    bufferedReader.close();
                if (bufferedWriter != null)
                    bufferedWriter.close();

             catch (IOException e) 
                e.printStackTrace();
            
        
    

服务器（这应该是正确的，但我会添加它作为上下文）：

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;

public class Server2 
    public static void main(String[] args) throws IOException 
        Socket socket = null;
        InputStreamReader inputStreamReader = null;
        OutputStreamWriter outputStreamWriter = null;
        BufferedReader bufferedReader = null;
        BufferedWriter bufferedWriter = null;
        ServerSocket serverSocket = null;

        serverSocket = new ServerSocket(4321);

        while(true) 

            try
                socket = serverSocket.accept();
                inputStreamReader = new InputStreamReader(socket.getInputStream());
                outputStreamWriter = new OutputStreamWriter(socket.getOutputStream());

                bufferedReader = new BufferedReader(inputStreamReader);
                bufferedWriter = new BufferedWriter(outputStreamWriter);

                while(true) 
                    String msgFromClient = bufferedReader.readLine();

                    System.out.println("Client:" + msgFromClient);

                    bufferedWriter.write("MSG received!");
                    bufferedWriter.newLine();
                    bufferedWriter.flush();

                    if (msgFromClient.equalsIgnoreCase("Bye"));
                    break;
                

                socket.close();
                inputStreamReader.close();
                outputStreamWriter.close();
                bufferedReader.close();
                bufferedWriter.close();


             catch (IOException e) 
                e.printStackTrace();
            
        
    

【问题讨论】：

您不需要五次关闭。您只需要关闭BufferedWriter。当你关闭它时，其他所有东西都会自动关闭。

【参考方案1】：

在您的服务器中，您在此声明中有一个错误的;：

if (msgFromClient.equalsIgnoreCase("Bye")); // <-- HERE
break;

因此break; 语句总是无条件执行，在收到并响应第一条消息后终止连接。

你需要删除那个;:

if (msgFromClient.equalsIgnoreCase("Bye"))
    break;

【讨论】：

天哪，我真是瞎了眼！我快疯了，因为我知道循环应该有效，哈哈。我想我需要更仔细地检查我的工作