Command Line Interface Chat Application

About

This application is a simple implementation of a chat application. The only feature missing here is authentication. This chat application has a command line interface with the details of the message format present below.
There are two files in the src folder - server.py and client.py. The first file contains the code for the server end whereas the second file contains the code for the client end.

How to run the code?

Run the following command to start the server-
```
python3 server.py 
```
Run the following command to start a client system-
```
python3 client.py [USERNAME] [SERVER_IP]
```
Here, USERNAME is the client's username. This username can only contain alphanumeric [a-zA-Z1-9] characters.

SERVER_IP is the server's IP address for connection. For example- 127.0.0.1 (localhost)

Note

ALL can't be used as a client's username. It is a reserved keyword for broadcast messages.
Multiple clients can be started using the above mentioned command on same system.

Message format

For unicast messages, use
```
@[RECVR_USERNAME]: Message
```
Remember RECVR_USERNAME should be a legal username of a client connected to the user. Otherwise, error would be raised by the server side (ERROR 102).
If the format of the message is wrong, appropiate help will be printed.
For broadcast messages, use
```
@ALL: Message
```
Broadcast messages are visible to all the clients connected to the server.

Implementation details

Python is used for the implementation. Python's socket library is used for making TCP sockets.
To handle multiple clients, threads are used to run parallel processes. Python's threading library is used for making threads.
At client's end, two threads are used to separate the sending and listening sockets' processes.
Registration protocol is implemented to register client's sockets at server side.

Enjoy :)

Author

Name - Gaurav Jain
Entry Number - 2019CS10349

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