服务器（Python）-使用套接字的客户端（Java）通信

我尝试从服务器向客户端发送消息，客户端收到消息后，将消息发送回服务器，依此类推。问题在于用 python 接收消息。循环就卡在那里了。

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();
        }

    }

}

Python 代码没问题。问题是调用out.printJava 代码中的内容并不一定会导致您的消息立即通过套接字发送。添加

out.flush();

之后立马

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

强制通过套接字发送消息。 (flush https://docs.oracle.com/javase/8/docs/api/java/io/PrintWriter.html#flush--“刷新”流中所有尚未发送的数据。）然后 Python 应该能够正确接收它。