Socket server no longer works when a client leaves

Question

My program works fine until a client leaves. After the client leaves, I am getting an error which is on the host server,

Following is the code I am trying:

import socket
import threading

class ChatServer:

    clients_list = []

    last_received_message = ""

    def __init__(self):
        self.server_socket = None
        self.create_listening_server()

    def create_listening_server(self):
        self.server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        local_ip = '127.0.0.1'
        local_port = 10319
        # this will allow you to immediately restart a TCP server
        self.server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        # this makes the server listen to requests coming from other computers on the network
        self.server_socket.bind((local_ip, local_port))
        print("Listening for incoming messages..")
        self.server_socket.listen(5)
        self.receive_messages_in_a_new_thread()

    def receive_messages(self, so):
        while True:
            incoming_buffer = so.recv(256)
            if not incoming_buffer:
                break
            self.last_received_message = incoming_buffer.decode('utf-8')
            self.broadcast_to_all_clients(so)  # send to all clients
        so.close()

    def broadcast_to_all_clients(self, senders_socket):
        for client in self.clients_list:
            socket, (ip, port) = client
            if socket is not senders_socket:
                socket.sendall(self.last_received_message.encode('utf-8'))

    def receive_messages_in_a_new_thread(self):
        while True:
            client = so, (ip, port) = self.server_socket.accept()
            self.add_to_clients_list(client)
            print('Connected to ', ip, ':', str(port))
            t = threading.Thread(target=self.receive_messages, args=(so,))
            t.start()

    def add_to_clients_list(self, client):
        if client not in self.clients_list:
            self.clients_list.append(client)

if __name__ == "__main__":
    ChatServer()

The error (ConnectionResetError) is at incoming_buffer = so.recv(256) .

Does anyone know what is the wrong with above code?

Answer 1

There's nothing wrong with the code. You just need to use try / except to catch this error and break out of the loop.

Python has a socketserver module built-in that handles much of this overhead.