problemes avec sys.argv sur socket chat serveur en python

# import required modules
import sys # to manage outpouts and error messages
import socket # to create the chat server
import select # to manage the send methode

# main variables
HOST = '' # we will use 'localhost'
USERS_LIST = [] # to have a base for connected users
RECV_BUFFER = 4096 # max buffering
PORT = 7777 # remote port

def server():

    # setting up of the server
    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    server_socket.bind((HOST, PORT))
    server_socket.listen(10)
    USERS_LIST.append(server_socket)

    print('Starting up the chat server on : {0}').format(PORT)

    while 1: # while the server is running we try to intercept incoming connections
        read, write, error = select.select(USERS_LIST, [], [], 0)

        for sock in read:
            if sock == server_socket:
                conn, addr = server_socket.accept()
                USERS_LIST.append(conn)
                print('New connected user (%s, %s)' % addr)

                send(server_socket, conn, "[%s:%s] entered the chatroom\n" % conn)
            else:
                try:
                    data = sock.recv(RECV_BUFFER)
                    if data:
                        send(server_socket, sock, '\r' + '<' + str(sock.getpeername()) + '>' + data)
                    else:
                        if sock in USERS_LIST:
                            USERS_LIST.remove(sock)
                            send(server_socket, sock, 'The user (%s, %s) left the chatroom\n' % addr)
                except:
                    send(server_socket, sock, 'The user (%s, %s) left the chatroom\n' % addr)
                    continue

    server_socket.close()

def send(server, sock, data):
    for socket in USERS_LIST:
        if socket != server and socket != sock:
            try:
                socket.send(data)
            except:
                socket.close()
                if socket in USERS_LIST:
                    USERS_LIST.remove(socket)

if __name__ == '__main__':
    sys.exit(server())

import sys
import socket
import select

def client():

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

    HOST = sys.argv[1]
    PORT = sys.argv[2]

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

    try: # try to connect to the server
        sock.connect((HOST, PORT)) # tuple host;port
    except: # if there is a socket error...
        print('Unable to connect to the remote host: {0}').format(HOST)
        sys.exit()

    print("Now connected to the remote host: {0}").format(HOST)
    sys.stdout.write('<you> ')
    sys.stdout.flush()

    while 1:

        socket.list = [sys.stdin, sock]

        read, write, error = select.select(socket_list, [], [])

        for s in read:
            if s == sock:
                data = s.recv(4096)
                if not data:
                    print('disconnected from the server')
                    sys.exit()

                else:
                    sys.stdout.write(data)
                    sys.stdout.write('<you> ')
                    sys.stdout.flush()

            else:
                data = sys.stdin.readline()
                sock.send(data)
                sys.stdout.write('<you> ')
                sys.stdout.flush()

if __name__ == '__main__':
    sys.exit(client())

Unable to connect to the remote host: {0}
Traceback (most recent call last):
  File "chat_client.py", line 20, in client
    sock.connect((HOST, PORT)) # tuple host;port
TypeError: an integer is required (got type str)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "chat_client.py", line 53, in <module>
    sys.exit(client())
  File "chat_client.py", line 22, in client
    print('Unable to connect to the remote host: {0}').format(HOST)
AttributeError: 'NoneType' object has no attribute 'format'