Commands supported by the client

# NAME will set name. The server will reply with an error if the name

already exists

# GET$\_$NAMES will get all client names

# MSG will send to the client NAME

# EXIT will close the client and connection

Explanation

The NAME command allows you to determine a name for our customer. For

example, NAME A will set the name A for the client, so that messages

intended for A are now forwarded to it by the server. The server will answer it

with HELLO with the specified name. For example, HELLO A$.$ If the name A is

already occupied by another client, the server will reply that the name is taken.

A GET$\_$NAMES command will cause the server to send the client a list of all

client names that are connected to the server $($don$\text{'}$t forget to remove

disconnected clients$)$

An MSG command will send a message to the customer based on their name.

For example, MSG A HELLO will send HELLO to CLIENT A$.$ The server will first

add the sender$$s name; for example, if B sent the message to A$,$ then A will

receive B SENT HELLO.

An EXIT order will cause the customer to be disconnected closing the socket.

Example run

The following screens show the following:

$1.$ Client connects

$2.$ The client sets the name A

$3.$ Another Client connects

$4.$ The client sets the name B

$5.$ Client A checked which clients exist and received A B

$6.$ Client B disconnected

$7.$ Client A checked which customers exist and received A

$8.$ Another Client connects

$9.$ The client set the name B

$10.$ Client A checked which clients exist and received A B

$11.$ Client A sent a HELLO message to B

$12.$ Client B received the message along with a message from the server

that the message was sent from A

$13.$ Client B sent a HELLO message to A

$14.$ Client B disconnects.

$15.$ Client A disconnects.

General guidelines

Like the basic server exercise, you need to use a protocol file, which will

include a length field. The server and the client will use the length field in

communicating $($and not just recv$(1024)).$

If the server receives an unknown command, it will return an appropriate

message to the client that sent the message.

If the server is prompted to forward a message to a client that does not

exist, it will return an appropriate message to the client that sent the

message.

Server writing guidance

Using the server code in the textbook, the main difference is that you need

to write a function that handles messages coming from the client. It is

recommended to have a data structure that will link a socket to a client

name; a Python dictionary can be useful.

Client writing guidance

As you may recall, the recv and input functions are blocking, meaning that

the customer will wait for information before moving on$.$ This will prevent

the program from running properly because the client may not be able to

receive user input until they receive a notification, and vice versa $$ it will

not be possible to receive messages until the user has finished entering

input.

The solution consists of two parts.

Instead of the recv function, the client will use the select function. You

can set the timeout in seconds.

Instead of the input function, we import the msvcrt module $($an

important part of our skill is self$-$study of topics, explanations and

examples can be found on the Internet, so I am not attaching an

explanation$)$ Create code that receives a character at a time from the

user using the kbhit and getch functions, prints to the screen and after

receiving a line feed character $($Enter$)$ sends the message to the server.

Tip: When printing to the screen, use the flush$=$True parameter so that

each character prints immediately to the screen.

Verification expected result score if not achieved

Basic functions

Connection of $2$ clients at the same time The server receives the $2$ clients Grade $0$

Both clients execute NAME and then GET$\_$NAMES, their names appear in the list of clients they receive. The names of all customers are one word only, in English, case sensitive$,$ without special characters. Their names appear on the list of clients they receive Minus $30$

A client sends a message to another client, only one word without any space. The other client receives the word, including the correct name of the client who sent it$.$ Minus $30$

Client disconnects with EXIT. The server goes on running properly and does not crash or hang. Minus $30$

A client sends a message that is not one of the defined messages. The server does not crash Minus $20$

Application standardization

A client sends a one$-$word message to another client. The other client receives the message. Minus $10$

A client sends a message to himself.

The message is received, or the client receives a message that it is not possible to send a message to yourself $($think about the case and take care of it$).$ Minus $10$

A client manages to determine the same name as another client.

A message indicating that it is impossible, is displayed. Minus $20$

When the client disconnects, his name is deleted from the client list $($the