# Source: F. Sarker, S. Washington. "Learning Python Network Programming"

import socket
 
#HOST = '127.0.0.1' # Listen only to localhost
HOST = ''          # Listen to all interfaces

PORT = 4040
 
def create_listen_socket(host, port):
   """ Setup the sockets our server will receive connection 
   requests on """

   sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
   sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
   sock.bind((host, port))
   sock.listen(100)
   return sock
 
def recv_msg(sock):
    """ Wait for data to arrive on the socket, then parse into 
    messages using b'\0' as a message delimiter"""

    data = bytearray()
    msg = ''
    # Repeatedly read 4096 Bytes off the socket, storing the bytes
    # in data until we see a message delimiter
    while not msg:
        recvd = sock.recv(4096)
        if not recvd:
            # Socket has been closed prematurely
            raise ConnectionError()
        data = data + recvd
        if b'\0' in recvd:
            msg = data.rstrip(b'\0')
    msg = msg.decode('utf-8')
    return msg

def prep_msg(msg):
    """ Prepare a string to be sent as a message """
    msg += '\0'
    return msg.encode('utf-8')

def send_msg(sock, msg):
    """ Send string over a socet, preparing it first """
    data = prep_msg(msg)
    sock.sendall(data)