socket_server.py

#! /usr/bin/python3

# Socket server in python using select function
import socket, select

if __name__ == "__main__":
	CONNECTION_LIST = [] # list of socket clients
	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)
				#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)
					# echo back the client message
					if data:
						sock.send(str.encode('OK ... ' + bytes.decode(data)))
						# client disconnected, so remove from socket list
				except:
					broadcast_data(sock, "Client (%s, %s) is offline" % addr)
					print ("Client (%s, %s) is offline" % addr)
					sock.close()
					CONNECTION_LIST.remove(sock)
					continue
	
	# while loop over, close the server socket
	server_socket.close()