python messaging app code example

Example: how to make chat box using python

#Server Script
import socket 
import select 
import sys 
from thread import *

"""The first argument AF_INET is the address domain of the 
socket. This is used when we have an Internet Domain with 
any two hosts The second argument is the type of socket. 
SOCK_STREAM means that data or characters are read in 
a continuous flow."""
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 
server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) 

# checks whether sufficient arguments have been provided 
if len(sys.argv) != 3: 
	print("Correct usage: script, IP address, port number")
	exit() 

# takes the first argument from command prompt as IP address 
IP_address = str(sys.argv[1]) 

# takes second argument from command prompt as port number 
Port = int(sys.argv[2]) 

""" 
binds the server to an entered IP address and at the 
specified port number. 
The client must be aware of these parameters 
"""
server.bind((IP_address, Port)) 

""" 
listens for 100 active connections. This number can be 
increased as per convenience. 
"""
server.listen(100) 

list_of_clients = [] 

def clientthread(conn, addr): 

	# sends a message to the client whose user object is conn 
	conn.send("Welcome to this chatroom!") 

	while True: 
			try: 
				message = conn.recv(2048) 
				if message: 

					"""prints the message and address of the 
					user who just sent the message on the server 
					terminal"""
					print("<" + addr[0] + "> " + message )

					# Calls broadcast function to send message to all 
					message_to_send = "<" + addr[0] + "> " + message 
					broadcast(message_to_send, conn) 

				else: 
					"""message may have no content if the connection 
					is broken, in this case we remove the connection"""
					remove(conn) 

			except: 
				continue

"""Using the below function, we broadcast the message to all 
clients who's object is not the same as the one sending 
the message """
def broadcast(message, connection): 
	for clients in list_of_clients: 
		if clients!=connection: 
			try: 
				clients.send(message) 
			except: 
				clients.close() 

				# if the link is broken, we remove the client 
				remove(clients) 

"""The following function simply removes the object 
from the list that was created at the beginning of 
the program"""
def remove(connection): 
	if connection in list_of_clients: 
		list_of_clients.remove(connection) 

while True: 

	"""Accepts a connection request and stores two parameters, 
	conn which is a socket object for that user, and addr 
	which contains the IP address of the client that just 
	connected"""
	conn, addr = server.accept() 

	"""Maintains a list of clients for ease of broadcasting 
	a message to all available people in the chatroom"""
	list_of_clients.append(conn) 

	# prints the address of the user that just connected 
	print(addr[0] + " connected")

	# creates and individual thread for every user 
	# that connects 
	start_new_thread(clientthread,(conn,addr))	 

conn.close() 
server.close()

#Client Script
# Python program to implement client side of chat room. 
import socket 
import select 
import sys 

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 
if len(sys.argv) != 3: 
	print("Correct usage: script, IP address, port number")
	exit() 
IP_address = str(sys.argv[1]) 
Port = int(sys.argv[2]) 
server.connect((IP_address, Port)) 

while True: 

	# maintains a list of possible input streams 
	sockets_list = [sys.stdin, server] 

	""" There are two possible input situations. Either the 
	user wants to give manual input to send to other people, 
	or the server is sending a message to be printed on the 
	screen. Select returns from sockets_list, the stream that 
	is reader for input. So for example, if the server wants 
	to send a message, then the if condition will hold true 
	below.If the user wants to send a message, the else 
	condition will evaluate as true"""
	read_sockets,write_socket, error_socket = select.select(sockets_list,[],[]) 

	for socks in read_sockets: 
		if socks == server: 
			message = socks.recv(2048) 
			print(message)
		else: 
			message = sys.stdin.readline() 
			server.send(message) 
			sys.stdout.write("<You>") 
			sys.stdout.write(message) 
			sys.stdout.flush() 
server.close() 


# Server (host) should have the top server script and the clients should have the client script. Both are labelled with a comment