需要有关服务器-客户端套接字通信的一些帮助[重复]

Question

此问题已经在这里有了答案：

Socket problem - readline won't work properly（5个答案）

关闭6小时前。

我正在尝试在Java中的套接字上做一个练习，以使客户端与服务器通信，我不明白为什么服务器卡在读取中并且好像没有从客户端接收消息一样，实际上是由客户发送的。服务器正确查看了客户端，并且接受成功。怎么做？

服务器代码

ServerSocket server = null;
Socket client = null;
while(true) {
    try{
        server = new ServerSocket();
        server.bind(new InetSocketAddress("localhost", 2000));
        client = server.accept();
        break;
    } catch (Exception e) {
        // TODO: handle exception
        e.printStackTrace();
    }   
}

BufferedReader reader = null;
BufferedWriter writer = null;
try {
    reader = new BufferedReader(new InputStreamReader(client.getInputStream()));
    writer = new BufferedWriter(new OutputStreamWriter(client.getOutputStream()));
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

try {
    String message = null;
    while((message = reader.readLine()) != null) {
        System.out.println("Client send: " + message);
        String answer = "ok"; 
        writer.write(answer);
        writer.flush();

    }
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

try {
    writer.close();
    reader.close();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

客户代码

Socket socket = new Socket();
try {
    SocketAddress address = new InetSocketAddress("127.0.0.1",2000);
    socket.connect(address);
} catch (IOException e) {
    e.printStackTrace();
}

BufferedReader reader = null;
BufferedWriter writer = null;
try {       
    reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
    writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
try {
    String string = "hello";
    writer.write(string);
    writer.flush();
    System.out.print("sent");
    String message;
    while((message = reader.readLine()) != null) {
        System.out.println("Server send: " + message);
        break;
    }
}catch (SocketException e) {
    // TODO: handle exception
    System.out.println(e);

} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

try {
    writer.close();
    reader.close();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

Answer 1

我的MRE：

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

public class Foo {
    public static void main(String[] args) {
        new Thread(() -> ServerFun.someServerMethod()).start();
        try {
            Thread.sleep(200);
        } catch (InterruptedException e) {}
        new Thread(() -> ClientFun.someClientMethod()).start();
    }
}

class ClientFun {
    public static void someClientMethod() {
        Socket socket = new Socket();
        try {
            SocketAddress address = new InetSocketAddress("LocalHost", 2000);
            System.out.println("client socket address: " + address);
            socket.connect(address);
        } catch (IOException e) {
            e.printStackTrace();
        }

        BufferedReader reader = null;
        BufferedWriter writer = null;
        try {
            reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            String string = "hello";
            writer.write(string);
            writer.newLine();
            writer.flush();
            System.out.print("sent");
            String message;
            while ((message = reader.readLine()) != null) {
                System.out.println("Server send: " + message);
                break;
            }
        } catch (SocketException e) {
            System.out.println(e);
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            writer.close();
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class ServerFun {
    public static void someServerMethod() {
        ServerSocket server = null;
        Socket client = null;
        // !!while (true) {  // not needed for a single client
            try {
                server = new ServerSocket();
                server.bind(new InetSocketAddress("localhost", 2000));
                System.out.println("server socket: " + server.getInetAddress());
                client = server.accept();
                // !! break;
            } catch (Exception e) {
                e.printStackTrace();
                System.exit(-1);
            }
        // !! }
        BufferedReader reader = null;
        BufferedWriter writer = null;
        try {
            reader = new BufferedReader(new InputStreamReader(client.getInputStream()));
            writer = new BufferedWriter(new OutputStreamWriter(client.getOutputStream()));
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            String message = null;
            while ((message = reader.readLine()) != null) {
                System.out.println("Client send: " + message);
                String answer = "ok";
                writer.write(answer);
                writer.newLine();
                writer.flush();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            writer.close();
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

您需要发送新行以使readLine方法起作用。例如，

writer.write(answer);
writer.newLine();  // add this **********
writer.flush();

客户端和服务器都必须到位。或者，使用PrintWriter，然后单击out.println(answer);

我还必须使用“ localhost”来使客户端正常工作。

希望您在我们解决此问题时看到了MRE的实用程序。下次，我希望您能为我们创建一个，而不是强迫我们创建一个。

Answer 2

这是股票，因为它就像输入。如果要在服务器侦听客户端时执行其他操作，则等到有数据到达它时，才应使用多重编程。在一个红色的莱斯汀给客户，而其他的则做其他事情