python-socket-chat

This is a chat application that allows multiple users to send and receive messages in real-time.

Features

• Send and receive messages in real-time
• View the list of available users and their online status
• Send messages to a specific user
• Save chat history
• No multi-threading

Usage

Run the server

To run the server, use the following command:

python server.py

Run the chat app

After running the server, you can run the chat app using the following command:

python chatapp.py

Login

When you run the chat app, you will be prompted to enter your username and password. If the username and password are correct, you will be logged in and the chat window will appear.

There are 3 users already created, defined in the users.json file:

• User: Alice, password: 123

• User: Bob, password: 456

• User: Charlie, password: 789

Send a message

To send a message, simply click on the user you want to send a message to and type your message in the input field at the bottom of the window. Then press Enter or click the Send button.

The message will be displayed in the chat window on both the sender's and receiver's screens (if the receiver is online and she/he is not in the chat with anyone else).

The message will also be saved to a file called history.json in the same directory as the chat app.

Logout

To logout, simply close the chat app window.

How it works

The chat app uses the tkinter library for the GUI and the socket library for the network communication.

When you run the chat app, it connects to the server using a TCP socket. The server is responsible for handling the communication between clients.

The server keeps track of the logged-in users, their online status, transmits messages between users, and saves the chat history.

Data transmission between the client and the server is done using a simple protocol, which consists of the following steps:

• Construct a dictionary containing the message to be sent. Structure of the dictionary:

{
    "purpose": "login", # purpose of the message, e.g. login, send_message, exit, etc.

    # other fields depending on the purpose
}

• Convert the dictionary to a string, then encode it to bytes. Now we call it data.

• Construct a packet containing the length of data and data itself. Structure of the packet:

$<length_of_data><data>$

• The packet is now ready to be sent over the network, using the sendall method of the socket object.

The destination (server or client) reads the packet, extracts the length of data, reads data, and decodes it back to a dictionary. Then it processes the message according to the purpose field.

The chat app uses a simple polling mechanism to check for new messages and updates from the server. It sends a request to the server every 100 milliseconds to check for new messages and updates.

Requirements

• Python 3
• tkinter library (usually included in Python distributions)
• socket library (usually included in Python distributions)

References

• Tkinter
• Socket Programming in Python
• JSON