chat_server.py

import sys
import socket
import select

HOST = ""
SOCKET_LIST = []
RECV_BUFFER = 4096
PORT = 9009
CONVERSATION = ""

def chat_server():
	global CONVERSATION
	server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
	server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
	server_socket.bind((HOST, PORT))
	server_socket.listen(10)

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

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

	while True:
		try:
			# Get the list sockets which are ready to be read through select
			# 4th arg, time_out = 0 : poll and never block
			ready_to_read, ready_to_write, in_error = select.select(SOCKET_LIST, [], [], 0)

			for sock in ready_to_read:
				# A new connection request recieved
				if sock == server_socket:
					sockfd, addr = server_socket.accept()
					SOCKET_LIST.append(sockfd)
					print("Client (%s, %s) connected" % addr)

					broadcast(server_socket, sockfd, "[%s, %s] entered our chatting room\n" % addr)
				# A message from a client, not a new connection
				else:
					# Process data recieved from client
					try:
						# Recieving data from socket
						data = sock.recv(RECV_BUFFER)
						if data:
							# there is something in the socket
							# broadcast(server_socket, sock, "\r" + '[' + str(sock.getpeername()) + '] ' + data) # old
							broadcast(server_socket, sock, "\r" + data)
						else:
							# Remove the socket that's broken
							if sock in SOCKET_LIST:
								SOCKET_LIST.remove(sock)

							# at this stage, no data probably means the connection has been broken
							broadcast(server_socket, sock, "Client (%s, %s) is offline\n" % addr)
					except:
						broadcast(server_socket, sock, "Client (%s, %s) is offline\n" % addr)
						continue
		except KeyboardInterrupt:
			server_socket.close()
			sys.exit()

	server_socket.close()


# broadcast chat messages to all connected clients
def broadcast(server_socket, sock, message):
	for socket in SOCKET_LIST:
		# send the message only to peer
		if socket != server_socket and socket != sock:
			try:
				socket.send(message)
			except:
				# Broken socket connection
				socket.close()
				# Broken socket, remove it
				if socket in SOCKET_LIST:
					SOCKET_LIST.remove(socket)

if __name__ == "__main__":
	sys.exit(chat_server())