socket chat server & client

client.py

# Tcp Chat server

import socket, select

#Function to broadcast chat messages to all connected clients
def broadcast_data (sock, message):
    #Do not send the message to master socket and the client who has send us the message
    for socket in CONNECTION_LIST:
        if socket != server_socket and socket != sock :
            try :
                socket.send(message.encode())
            except :
                # broken socket connection may be, chat client pressed ctrl+c for example
                socket.close()
                CONNECTION_LIST.remove(socket)

if __name__ == "__main__":

    # List to keep track of socket descriptors
    CONNECTION_LIST = []
    RECV_BUFFER = 4096 # Advisable to keep it as an exponent of 2
    PORT = 5000

    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    # this has no effect, why ?
    server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    server_socket.bind(("0.0.0.0", PORT))
    server_socket.listen(10)

    # Add server socket to the list of readable connections
    CONNECTION_LIST.append(server_socket)

    print("Chat server started on port " + str(PORT))

    while 1:
        # Get the list sockets which are ready to be read through select
        read_sockets,write_sockets,error_sockets = select.select(CONNECTION_LIST,[],[])

        for sock in read_sockets:
            #New connection
            if sock == server_socket:
                # Handle the case in which there is a new connection recieved through server_socket
                sockfd, addr = server_socket.accept()
                CONNECTION_LIST.append(sockfd)
                print("Client (%s, %s) connected" % addr)
                print(CONNECTION_LIST)
                print(type(CONNECTION_LIST))

                broadcast_data(sockfd, "[%s:%s] entered room\n" % addr)

            #Some incoming message from a client
            else:
                # Data recieved from client, process it
                try:
                    #In Windows, sometimes when a TCP program closes abruptly,
                    # a "Connection reset by peer" exception will be thrown
                    data = sock.recv(RECV_BUFFER).decode()
                    if data:
                        broadcast_data(sock, "\r" + '<' + str(sock.getpeername()) + '> ' + data)

                except:
                    broadcast_data(sock, "Client (%s, %s) is offline" % addr)
                    print("Client (%s, %s) is offline" % addr)
                    sock.close()
                    try:
                        CONNECTION_LIST.remove(sock)
                    except:
                        print(CONNECTION_LIST)
                        continue
                    continue

    server_socket.close()

server.py

# telnet program example
import socket, select, string, sys

def prompt() :
    sys.stdout.write('<You> ')
    sys.stdout.flush()

#main function
if __name__ == "__main__":

    if(len(sys.argv) < 3) :
        print('Usage : python telnet.py hostname port')
        sys.exit()

    host = sys.argv[1]
    port = int(sys.argv[2])

    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.settimeout(2)

    # connect to remote host
    try :
        s.connect((host, port))
    except :
        print('Unable to connect')
        sys.exit()

    print('Connected to remote host. Start sending messages')
    prompt()

    while 1:
        rlist = [sys.stdin, s]

        # Get the list sockets which are readable
        read_list, write_list, error_list = select.select(rlist , [], [])

        for sock in read_list:
            #incoming message from remote server
            if sock == s:
                data = sock.recv(4096).decode()
                if not data :
                    print('\nDisconnected from chat server')
                    sys.exit()
                else :
                    #print data
                    sys.stdout.write(data)
                    prompt()

            #user entered a message
            else :
                msg = sys.stdin.readline()
                s.send(msg.encode())
                prompt()