Forwarding on TCP connection $(50$ Points$)$

Figure $1.$ Architecture of Forwarder

We will use three python codes $--(1)$ TCP server, $(2)$ TCP client, and $(3)$

forwarder.py $($a combination of

TCP client and server as illustrated above$).$ Utilize the TCP server and client codes designed in project $3.$

Design $"$

forwarder.py$"$ as the following:

A TCP server must start first and wait for a forwarder. The forwarder contains TCP server and clients.

A TCP client in the forwarder will establish a connection to the TCP server. For this connection, you

must use a TCP client in the forwarder. $(25$ Points$)$

Once your forwarder is connected to the TCP server, the TCP server in the forwarder will start and

then, a TCP client must start. If you type a word on the TCP client, the TCP client will send this word

to the forwarder. The forwarder will forward this word to the TCP server as shown in Figure $1(25$

points$)$

TCP$\_$Client Code:

import socket

import threading

def receive$\_$messages$($sock$)$:

while True:

try:

message $=$ sock.recv$(1024).$decode$(\text{'}$utf$-8\text{'})$

if message:

print$($message$)$

else:

print$("$Disconnected from server"$)$

break

except:

print$("$An error occurred. Disconnecting..."$)$

sock.close$()$

break

def send$\_$messages$($sock$)$:

while True:

message $=$ input$(\text{'}\text{'})$

try:

sock.send$($message$.$encode$(\text{'}$utf$-8\text{'}))$

if message.lower$()==$ 'exit':

break

except:

print$("$An error occurred. Disconnecting..."$)$

sock.close$()$

break

def main$($server$\_$ip$,$ server$\_$port$)$:

sock $=$ socket.socket$($socket$.$AF$\_$INET, socket.SOCK$\_$STREAM$)$

try:

sock.connect$(($server$\_$ip$,$ server$\_$port$))$

print$("$Connected to server"$)$

# Start the thread for receiving messages

threading.Thread$($target$=$receive$\_$messages, args$=($sock$,)).$start$()$

send$\_$messages$($sock$)$

except Exception as e:

print$($f$"$Failed to connect to server: $\{$e$\}")$

finally:

sock.close$()$

if $\_\_$name$\_\_=="\_\_$main$\_\_"$:

SERVER$\_$IP $=$ "localhost"

SERVER$\_$PORT $=10000$

main$($SERVER$\_$IP$,$ SERVER$\_$PORT$)$

TCP$\_$SERVER Code:

from socket import $*$

import threading

import sys

PORT $=10000$

clients $=\{\}$

def broadcast$\_$message$($message$,$ sender$\_$id$)$:

for id$,$ client in clients.items$()$:

if id $!=$ sender$\_$id:

try:

client.send$($message$)$

except:

# Removing the client if it's no longer connected

del clients$[$id$]$

def handler$($clientsock$,$ addr$)$:

# Prompting new client for an identifier

clientsock.send$($b$\text{'}$Enter your ID:$\text{'})$

id $=$ clientsock.recv$(1024).$decode$().$strip$()$

clients$[$id$]=$ clientsock # Adding the client with its ID

while True:

try:

data $=$ clientsock.recv$(1024)$

if not data:

break

sys$.$stderr.write$($f$\text{'}\{$id$\}$ sent $"\{$data$.$decode$()\}"$

$\text{'})$

# Broadcasting received message to other clients, including sender$\text{'}$s ID

message $=$ f$"\{$id$\}$: $\{$data$.$decode$()\}".$encode$()$

broadcast$\_$message$($message$,$ id$)$

if "exit" $==$ data.decode$().$strip$().$lower$()$:

break

except ConnectionResetError:

break

# Removing the client on disconnect

del clients$[$id$]$

clientsock.close$()$

sys$.$stderr.write$($f$"$Closed connection with $\{$id$\}$

$")$

def start$\_$server$()$:

server$\_$address $=(\text{'}$localhost$\text{'},$ PORT$)$

serversock $=$ socket$($AF$\_$INET, SOCK$\_$STREAM$)$

serversock.setsockopt$($SOL$\_$SOCKET, SO$\_$REUSEADDR, $1)$

serversock.bind$($server$\_$address$)$

sys$.$stderr.write$(\text{'}$Server starting up

$\text{'})$

serversock.listen$(5)$ # Listening for up to $5$ clients

while True:

sys$.$stderr.write$(\text{'}$Waiting for connection...

$\text{'})$

clientsock, client$\_$address $=$ serversock.accept$()$

sys$.$stderr.write$($f$\text{'}$Client connected: $\{$client$\_$address$\}$

$\text{'})$

x $=$ threading.Thread$($target$=$handler, args$=($clientsock$,$ client$\_$address,$))$

x$.$start$()$

start$\_$server$()$