Creating a simple Chat application in Python (Sock

问题:

I'm trying to create a simple chat application using sockets (python). Where a client can send a message to server and server simply broadcast the message to all other clients except the one who has sent it.

Client has two threads, which are running forever

send: Send simply sends the cleints message to server.

receive: Receive the message from the server.

Server also has two threads, which are running forever

accept_cleint: To accept the incoming connection from the client.

broadcast_usr: Accepts the message from the client and just broadcast it to all other clients.

But I'm getting erroneous output (Please refer the below image). All threads suppose to be active all the times but Some times client can send message sometimes it can not. Say for example Tracey sends 'hi' 4 times but its not broadcasted, When John says 'bye' 2 times then 1 time its message gets braodcasted. It seems like there is some thread synchronization problem at sever, I'm not sure. Please tell me what's wrong.

Below is the code.

chat_client.py

import socket, threading

def send():
    while True:
        msg = raw_input('\nMe > ')
        cli_sock.send(msg)

def receive():
    while True:
        sen_name = cli_sock.recv(1024)
        data = cli_sock.recv(1024)

        print('\n' + str(sen_name) + ' > ' + str(data))

if __name__ == "__main__":   
    # socket
    cli_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    # connect
    HOST = 'localhost'
    PORT = 5023
    cli_sock.connect((HOST, PORT))     
    print('Connected to remote host...')
    uname = raw_input('Enter your name to enter the chat > ')
    cli_sock.send(uname)

    thread_send = threading.Thread(target = send)
    thread_send.start()

    thread_receive = threading.Thread(target = receive)
    thread_receive.start()

chat_server.py

import socket, threading

def accept_client():
    while True:
        #accept    
        cli_sock, cli_add = ser_sock.accept()
        uname = cli_sock.recv(1024)
        CONNECTION_LIST.append((uname, cli_sock))
        print('%s is now connected' %uname)

def broadcast_usr():
    while True:
        for i in range(len(CONNECTION_LIST)):
            try:
                data = CONNECTION_LIST[i][1].recv(1024)
                if data:
                    b_usr(CONNECTION_LIST[i][1], CONNECTION_LIST[i][0], data)
            except Exception as x:
                print(x.message)
                break

def b_usr(cs_sock, sen_name, msg):
    for i in range(len(CONNECTION_LIST)):
        if (CONNECTION_LIST[i][1] != cs_sock):
            CONNECTION_LIST[i][1].send(sen_name)
            CONNECTION_LIST[i][1].send(msg)

if __name__ == "__main__":    
    CONNECTION_LIST = []

    # socket
    ser_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    # bind
    HOST = 'localhost'
    PORT = 5023
    ser_sock.bind((HOST, PORT))

    # listen    
    ser_sock.listen(1)
    print('Chat server started on port : ' + str(PORT))

    thread_ac = threading.Thread(target = accept_client)
    thread_ac.start()

    thread_bs = threading.Thread(target = broadcast_usr)
    thread_bs.start()

回答1:

Ok I lied in my comment earlier, sorry. The issue is actually in the broadcast_usr() function on the server. It is blocking in the recv() method and preventing all but the currently selected user from talking at a single time as it progresses through the for loop. To fix this, I changed the server.py program to spawn a new broadcast_usr thread for each client connection that it accepts. I hope this helps.

import socket, threading

def accept_client():
    while True:
        #accept    
        cli_sock, cli_add = ser_sock.accept()
        uname = cli_sock.recv(1024)
        CONNECTION_LIST.append((uname, cli_sock))
        print('%s is now connected' %uname)
        thread_client = threading.Thread(target = broadcast_usr, args=[uname, cli_sock])
        thread_client.start()

def broadcast_usr(uname, cli_sock):
    while True:
        try:
            data = cli_sock.recv(1024)
            if data:
                print "{0} spoke".format(uname)
                b_usr(cli_sock, uname, data)
        except Exception as x:
            print(x.message)
            break

def b_usr(cs_sock, sen_name, msg):
    for client in CONNECTION_LIST:
        if client[1] != cs_sock:
            client[1].send(sen_name)
            client[1].send(msg)

if __name__ == "__main__":    
    CONNECTION_LIST = []

    # socket
    ser_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    # bind
    HOST = 'localhost'
    PORT = 5023
    ser_sock.bind((HOST, PORT))

    # listen    
    ser_sock.listen(1)
    print('Chat server started on port : ' + str(PORT))

    thread_ac = threading.Thread(target = accept_client)
    thread_ac.start()

    #thread_bs = threading.Thread(target = broadcast_usr)
    #thread_bs.start()

回答2:

I tried to get around the bug you said @Atinesh. The client will be asked a username once and this 'uname' will be included in the data to be sent. See what I did to the 'send' function.

For easier visualization, I added a '\t' to all received messages.

import socket, threading

def send(uname):
    while True:
        msg = raw_input('\nMe > ')
        data = uname + '>' + msg
        cli_sock.send(data)

def receive():
    while True:
        data = cli_sock.recv(1024)
        print('\t'+ str(data))

if __name__ == "__main__":   
    # socket
    cli_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    # connect
    HOST = 'localhost'
    PORT = 5023

    uname = raw_input('Enter your name to enter the chat > ')

    cli_sock.connect((HOST, PORT))     
    print('Connected to remote host...')


    thread_send = threading.Thread(target = send,args=[uname])
    thread_send.start()

    thread_receive = threading.Thread(target = receive)
    thread_receive.start()

You also have to modify your server code accordingly.

server.py

import socket, threading

def accept_client():
    while True:
        #accept    
        cli_sock, cli_add = ser_sock.accept()
        CONNECTION_LIST.append(cli_sock)
        thread_client = threading.Thread(target = broadcast_usr, args=[cli_sock])
        thread_client.start()

def broadcast_usr(cli_sock):
    while True:
        try:
            data = cli_sock.recv(1024)
            if data:
               b_usr(cli_sock, data)
         except Exception as x:
            print(x.message)
            break

def b_usr(cs_sock, msg):
    for client in CONNECTION_LIST:
        if client != cs_sock:
            client.send(msg)

if __name__ == "__main__":    
    CONNECTION_LIST = []

    # socket
    ser_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    # bind
    HOST = 'localhost'
    PORT = 5023
    ser_sock.bind((HOST, PORT))

    # listen    
    ser_sock.listen(1)
    print('Chat server started on port : ' + str(PORT))

    thread_ac = threading.Thread(target = accept_client)
    thread_ac.start()

The things that changed in the server side are: the user who connected and the user who spoke is not seen anymore. I don't know if it would mean that much if your purpose is to connect clients. Maybe if you want to strictly monitor clients via the server, there could be another way.