如何在 Java 客户端服务器程序中从控制台获取输入

Question

我写了一个简单的客户端服务器程序。我能够将文本从客户端发送到服务器，反之亦然。但是在客户端打印服务器的数据后，我无法在客户端的CLI上打印任何东西。

我不确定我做错了什么。我怀疑注释 "Bug Here" 行中的错误。我找不到这些行中的问题。

请在下面找到我的代码。

ATMClient.java

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

public class ATMClient
{
    public static void main(String args[])
    {
        try
        {
            Socket sock = new Socket("localhost", 9010);
            sock.setSoTimeout(10000);
            System.out.println("Connection established");
            String data = null;

            InputStreamReader input = new InputStreamReader(sock.getInputStream());
            BufferedReader bread = new BufferedReader(input);

            BufferedReader brCli = new BufferedReader(new InputStreamReader(System.in));
            System.out.print("Enter text to be sent to Server: ");
            String strCli = brCli.readLine();

            PrintWriter pwrite = new PrintWriter(sock.getOutputStream(), true);
            pwrite.println(strCli);

        // Bug Here: The control in not coming out of the while loop
            while((data = bread.readLine()) != null)
            {
                System.out.println(data);
            }

        // Bug Here: The following line does not get printed.
            System.out.print("Enter an Option: ");

            pwrite.close();
            bread.close();
            input.close();
        }
        catch(IOException ex)
        {
            System.err.println(ex);
        }
    }
}

ATMServer.java

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

public class ATMServer
{
    public static void main(String args[])
    {
        try
        {
            ServerSocket server = new ServerSocket(9010);
            Socket client = server.accept();
            System.out.println("Connection Established");

            InputStream input = client.getInputStream();
            BufferedReader bufread = new BufferedReader(new InputStreamReader(input));

            PrintWriter pwrite = new PrintWriter(client.getOutputStream(), true);

            pwrite.println("1. Deposit");
            pwrite.println("2. Withdrawal");
            pwrite.println("3. Balance");
            pwrite.println("4. Exit");

            String data = null;
            while((data = bufread.readLine()) != null)
            {
                System.out.println(data);
            }

            pwrite.close();
            bufread.close();
            input.close();
            server.close();
            client.close();
        }
        catch(Exception ex)
        {
            System.err.println(ex);
        }
    }
}

输出：

user1$ java ATMServer
Connection Established
hello

user1$ java ATMClient
Connection established
Enter text to be sent to Server: hello
1. Deposit
2. Withdrawal
3. Balance
4. Exit
Deposit
^C user1$

你能帮我弄清楚如何在客户端的控制台上获取输入吗？谢谢

Answer 1

只要来自远程套接字的输入流是打开的， bread.readLine() 永远不会 return null, 因此这个循环永远不会结束：

while((data = bread.readLine()) != null)
{
    System.out.println(data);
}

您需要添加某种信号，例如文本 "ENDMSG"。服务器应该在完成与客户端的对话后发送它，并且客户端应该这样识别它，并退出循环。例如：

while((data = bread.readLine()) != null)
{
    if (data.equals("ENDMSG")) {
        break;
    }
    System.out.println(data);
}

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