服务器（Python） - 使用套接字的客户端（Java）通信 [英] Server(Python) - Client(Java) communication using sockets

问题描述

我尝试从服务器向客户端发送消息，在客户端收到消息后，它会向服务器发回消息，依此类推。问题是在python中接收消息。它被卡在那里。

I try to send a message from server to a client, after client receives the message, it sends back a message to the server and so on. The problem is with receiving the message in python. The loop it's stuck there.

import socket

HOST = "localhost"
PORT = 9999
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print('Socket created')

try:
    s.bind((HOST, PORT))
except socket.error as err:
    print('Bind failed. Error Code : ' .format(err))
s.listen(10)
print("Socket Listening")
conn, addr = s.accept()
while(True):
    conn.send(bytes("Message"+"\r\n",'UTF-8'))
    print("Message sent")
    data = conn.recv(1024)
    print(data.decode(encoding='UTF-8'))

---

---

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;


public class Main {
    static Thread sent;
    static Thread receive;
    static Socket socket;

    public static void main(String args[]){
            try {
                socket = new Socket("localhost",9999);
            } catch (UnknownHostException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            sent = new Thread(new Runnable() {

                @Override
                public void run() {
                    try {
                        BufferedReader stdIn =new BufferedReader(new InputStreamReader(socket.getInputStream()));
                        PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
                        while(true){
                            System.out.println("Trying to read...");
                                String in = stdIn.readLine();
                                System.out.println(in);
                                out.print("Try"+"\r\n");
                                System.out.println("Message sent");
                            }

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


                }
            });
        sent.start();
        try {
            sent.join();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

}

推荐答案

Python代码很好。问题是在Java代码中调用 out.print 并不一定会导致您的消息立即通过套接字发送。添加

The Python code is fine. The problem is that calling out.print in the Java code does not necessarily cause your message to be sent through the socket immediately. Add

out.flush();

紧跟在

out.print("Try"+"\r\n");

强制通过套接字发送消息。 （ flush 通过流刷新尚未发送的任何数据。）Python应该能够正确接收它。

to force the message to be sent through the socket. (flush "flushes" through the stream any data that has not yet been sent.) The Python should then be able to receive it correctly.

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