Code written in Python $3\mathrm{.}13$ and must be stored in files named

server.py and client.py$.$ Code must be stored in files named

server.py and client.py$.$ You must use the $$socket$$ library directly $($i$.$e$.,$ not via any other

Python module$)$ for network communications. You are required to implement a client$-$server system, which implements an instant messenger using TCP allowing users to chat with each other. This instant messenger will consist of a client and a server program. You should be able to invoke server and client as

follows:

python server.py $[$port$]$

python client.py $[$username$][$hostname$][$port$]$

$1)$ The server and clients should implement the following functionality :

$$ When a Client connects, on the Server, print where the connection is coming from

$($including the IP address and the port number of the Client$).$

$$ When a Client connects, on the Client, display a simple welcome message from the

server. Note that this message must be sent over a network socket and should not be

hardcoded on the client side.

$$ Allow multiple Clients to connect to the same Server. On each Client, provide an

input prompt allowing the Client to send messages.

$$ Use the username passed to client.py to print $[$username$]$ has joined$$ on all

connected Clients whenever a client connects to the Server.

$$ Allow Client to leave the system by implementing a command. Use the username

passed to client.py to print $[$username$]$ has left$$ on all other connected Clients.

$$ Allow Client to leave the system unexpectedly. Use the username passed to client.py

to print $[$username$]$ has left$$ on all other connected Clients.

$$ One of the connected clients disconnecting should not cause the server to crash.

$2)$ Messaging functions :

$$ Client should be able to send multiple messages.

$$ Client should be able to broadcast messages to all other clients. Broadcast means that

a message is sent to all other clients excluding the one that sends the message.

$$ Client should be able to unicast messages to another client individually when there

are more than two clients in the system. Unicast means to send messages to a single

client.

$$ Client should be able to change between the above messaging modes.

$$ Server has a $$SharedFiles$$ folder. Clients should be able to access this folder by

implementing a command. You may consider using the environment variable

SERVER$\_$SHARED$\_$FILES to find this folder. Server replies with a successful

access message $($including the number of files in the folder$)$ via the connection socket

$($not hardcoded$)$ that can display on a Client prompt.

$$ Once Clients access this $$SharedFiles$$ folder, a list of files in this folder will be

displayed on Client prompt.

$$ Client can download any files $($text$,$ image, audio, video$)$ from the $$SharedFiles $$

folder. Downloaded files should be put in a folder named by the username of Client.

Note that the file itself must be sent over a network socket and should not be

hardcoded on the client side.

$$ Display the size $($in bytes$)$ for each downloaded file on Client prompt. Note that this

must be sent over a network socket and should not be hardcoded on the client side.

$3)$ Error $/$ Exception Handling

Any errors that can occur on either client or server side should be handled appropriately.

Especially watch out for the following:

$$ In case of a crash, attempt to close remaining connections and print an error message

in the terminals of all previous connected devices.

$$ The server should not allow any client to transmit messages without having first set

a username.

$$ If the server is not available or port$/$hostname are wrong, an error message detailing

the issue should be printed.