Python Socket - Server Stop after receive only one message

Question

firstly sorry for my bad english (I'm French) because I'm trying to not use Google Translate.

So, my problem is in the following set of server.py and client.py. Just a client that send every 10 seconds a message with a incremental counter on the server.py. I write this script to check if my university work server "live" or "die" after my logout (and for my training).

server.py:

# -*- coding: utf-8 -*-

import socket

HOST = 'localhost'
PORT = 1602

socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
socket.bind(('localhost', PORT))

while True:
        socket.listen(5)
        client, address = socket.accept()
        print(f"{address} connected")

        response = client.recv(1024)
        print(response.decode())

print("Close")
client.close()
socket.close()

client.py:

# -*- coding: utf-8 -*-

import socket
from apscheduler.schedulers.blocking import BlockingScheduler

HOST = 'localhost'
PORT = 1602

socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
socket.connect((HOST, PORT))
print(f"Connection on {PORT}")

timeCount = 0

def some_job():
    global timeCount
    timeCount += 1

    print(f"Send N°{timeCount}")
    string = f'Schedule Transmission N°{timeCount}'
    socket.send(f"Schedule Transmission N°{timeCount}".encode())

scheduler = BlockingScheduler()
scheduler.add_job(some_job, 'interval', seconds=5)
scheduler.start()

print("Close")
socket.close()

The problem is that the server side print only (and probably receive only) the first message/first transmission. So, not a problem of encodage and the connexion seems to exist even after the first message print. I understand well the code in itself. I don't see what's the problem. There is any exception or error when running.

Can someone help me, please?

Cordially

You need a nested loop to keep reading messages until it gets EOF. — Barmar, Sep 17 '21 at 19:25
You can also use multi-threading. When a client connects, spawn a thread to process that socket while the original thread waits for new connections. — Barmar, Sep 17 '21 at 19:26
@lechat-marcellin You should move socket.listen() to outside of infinite loop. It is enough to be called once to mark the socket for listening. — sigkilled, Sep 17 '21 at 20:06
@sigkilled Thanks. Even if that was not the problem in my code, it's interesting to know that for my training. — Lechat Marcellin, Sep 17 '21 at 20:33

score 2 · Accepted Answer · answered Sep 17 '21 at 19:46

I only needed to change your server code. I added multithreading. Now multible clients can connect to the server without blocking the entire process.

# -*- coding: utf-8 -*-

import socket
import threading

HOST = 'localhost'
PORT = 1602

socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
socket.bind(('localhost', PORT))

def handle_client(client, addr):
    print(f"[NEW CONNECTION] {addr} connected.")
    connected = True
    while connected:
        response = client.recv(1024)
        if response:
            print(f"[{addr}] {response.decode()}")

    client.close()
    

while True:
    socket.listen()
    client, addr = socket.accept()
    thread = threading.Thread(target=handle_client, args=(client, addr))
    thread.start()

Thank you. This code indeed work very well and I will use it. However, isn't there a way to solve the problem and achieve the same result without Multithreading and just Socket? It's just for my knowledge and my training. — Lechat Marcellin, Sep 17 '21 at 20:37

Python Socket - Server Stop after receive only one message

1 Answers1