Question

The following must be coded using Python programming language:

In this assignment you will implement two programs: a chat client and a server. The server will listen to a known port for new connections from clients. When a client connects, it will be able to authenticate with the server and then join a chat room and send messages.

Answer 1

1. chat_server.py

import sys, socket, select

HOST = ''
SOCKET_LIST = []
RECV_BUFFER = 4096
PORT =4713

def chat_server():

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 1:

# 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:
# receiving data from the socket.
data = sock.recv(RECV_BUFFER)
if data:
# there is something in the socket
broadcast(server_socket, sock, "\r" + '[' + str(sock.getpeername()) + '] ' + data)
else:
# remove the socket that's broken
if sock in SOCKET_LIST:
SOCKET_LIST.remove(sock)

# at this stage, no data means probably the connection has been broken
broadcast(server_socket, sock, "Client (%s, %s) is offline\n" % addr)

# exception
except:
broadcast(server_socket, sock, "Client (%s, %s) is offline\n" % addr)
continue

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())

2. chat_client.py

import sys, socket, select

def chat_client():
if(len(sys.argv) < 3) :
print 'Usage : python chat_client.py hostname port'
sys.exit()

host = sys.argv[1]
port = int(sys.argv[2])

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(2)

# connect to remote host
try :
s.connect((host, port))
except :
print 'Unable to connect'
sys.exit()

# TEST
person = raw_input ('Please enter your username: ')
print 'Connected to remote host. You can start sending messages.'
sys.stdout.write( person + '[Me]: ' ); sys.stdout.flush()

while 1:
socket_list = [sys.stdin, s]

# Get the list sockets which are readable
read_sockets, write_sockets, error_sockets = select.select(socket_list , [], [])

for sock in read_sockets:
if sock == s:
# incoming message from remote server, s
data = sock.recv(4096)
if not data :
print '\nDisconnected from chat server'
sys.exit()
else :
#print data
sys.stdout.write(data)
sys.stdout.write( person + '[Me]: '); sys.stdout.flush()   
  
else :
# user entered a message
msg = sys.stdin.readline()
s.send(msg)
sys.stdout.write( person + '[Me]: '); sys.stdout.flush()

if __name__ == "__main__":

sys.exit(chat_client())

Please let me know if you need anything from my end regarding this program.