# Import the required python components

import socket, select, sys

#Command for exiting system

QUITCOMMAND = "#quit"

#Port number is a constant

PORT = 3000

#Initilize buffersize

bufferSize = 4096

# Used to add prefix to messages before printing

msgPrefix = ''

# Implement a socket

def implementSocket(address):

clientConnection = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

clientConnection.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

clientConnection.connect((address, PORT))

return clientConnection

#Validate user's command to run the client host

if len(sys.argv) < 2:

# Print invalid commend and standard error

print("Invalid command! Write into cmd: Python3 chatClient.py [hostIP address]", file = sys.stderr)

# Exit system because of improper command

sys.exit(1)

# Create a connection if user's command is correct

else:

# Implement a socket

clientConnection = implementSocket(sys.argv[1])

# Print success message

print("Connected to server\n")

# Holds the list of connections

connectionList = [sys.stdin, clientConnection]

# Create an infinite loop

while True:

#Waiting until ready for reading, wait until ready for writing, wait for an "exceptional condition"

userRead, userWrite, socketErr = select.select(connectionList, [], [])

# Iterate through the available socket that needs to be read

for userSocket in userRead:

# A Response received from server

if userSocket is clientConnection:

# Get message from server

msg = userSocket.recv(bufferSize)

# If the server is down

if not msg:

#Print error and exit script

print("Server is down! Sorry for your inconvinience!!!")

sys.exit(2)

# else the server is working, print then wait for user to add command

else:

# Client leaves Lobby on server

if msg == QUITCOMMAND.encode():

sys.stdout.write('You have left the lobby, good bye.\n')

sys.exit(2)

else:

# Decode message from server

sys.stdout.write(msg.decode())

# If the user is new, add the name command

if 'Enter your screen name:' in msg.decode():

# add messge

msgPrefix = 'name: '

# Prompt the usre for a command

else:

msgPrefix = '> '

print('>', end=' ', flush = True)

# User sends commands and messages to server

else:

# Get user input

msg = msgPrefix + sys.stdin.readline()

# Send message to server

clientConnection.sendall(msg.encode())