Design a Chat application using python which has the following features: o It sh
ID: 3775795 • Letter: D
Question
Design a Chat application using python which has the following features:
o It should use connection orient reliable Transport layer protocol o Chat Application follows client and multithreaded server architecture o Chat Room: Chat Messages are sent from everybody to everybody. o Standard message header: Notice that use of standard header will make applications developed by different users to be compatible with each other. Note that messages in only below format will be exchanged between server and client. Your application header must follow following field structure in the order of appearance. Following is the header structure in tuple format (Header Field, Header Size, description) UNameL, 2 Bytes, Length of username in bytes MessageL, 4 bytes, Length of message Username, n, Username Message, n, Message o Client Side User given parameters: IP address, port number, Username Note: any one is able to connect to any server
o Clients can come and go, when a new client (user) arrives the server should broadcast a message to all the clients with a message that someone has logged in and broadcast a message if server realizes someone has left. Server periodically displays a list of users.
Explanation / Answer
import socket, select
#Function to broadcast chat messages to all connected clients
def broadcast_data (sock, message):
#Do not send the message to master socket and the client who has send us the message
for socket in CONNECTION_LIST:
if socket != server_socket and socket != sock :
try :
socket.send(message)
except :
# broken socket connection may be, chat client pressed ctrl+c for example
socket.close()
CONNECTION_LIST.remove(socket)
if __name__ == "__main__":
# List to keep track of socket descriptors
CONNECTION_LIST = []
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
broadcast_data(sockfd, "[%s:%s] entered room " % 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)
if data:
broadcast_data(sock, " " + '<' + str(sock.getpeername()) + '> ' + data)
except:
broadcast_data(sock, "Client (%s, %s) is offline" % addr)
print "Client (%s, %s) is offline" % addr
sock.close()
CONNECTION_LIST.remove(sock)
continue
server_socket.close()