Introduction

Websocket is a bidirectional communication protocol. In traditional rest api, client-server communication is a uni-direction protocol. i.e. in a single communication channel request will be sent and a response will be received. To send another request new tcp connection has to be established. But as in Websocket communication, over a single TCP communication, multiple messages can be exchanged.

We will implement the same using Python. For this, we will use Python packages

Follow the below steps to create client and server communication step-by-step.

Step 1. Create a directory for the project and type the below command to create a virtual environment for your project.

pipenv shell

Step 2. Install packages required.

pipenv install websockets
pipenv install asyncio

Step 3. Create a sample py file for the server, and add the below code.

import websockets
import asyncio
 
# Creating WebSocket server
async def ws_server(websocket):
    print("WebSocket: Server Started.")
 
    try:
        while True:
            # Receiving values from client
            endpoint_with_input = await websocket.recv()
 
            # Prompt message when any of the field is missing
            if endpoint_with_input == "":
                print("Error Receiving Value from Client.")
                break
 
            # Printing details received by client
            print("Details Received from Client:")
            print(f"endpoint_with_input: {endpoint_with_input}")

            data = endpoint_with_input.split(" ")
            endpoint = data[0]
            print("endpoint : ", endpoint)

            params =  data[1:]
            print("params : ", str(params))

            if endpoint == "add":
                _result = int(params[0]) + int(params[1])

            elif endpoint == "sub":
                _result = int(params[0]) - int(params[1])

            elif endpoint == "mul":
                _result = int(params[1]) * int(params[0])
            
            else:
                _result = "endpoint not found"

            await websocket.send(f"Result {_result}")
            print("==========================")
 
    except websockets.ConnectionClosedError:
        print("Internal Server Error.")
 
 
async def main():
    async with websockets.serve(ws_server, "localhost", 7890):
        await asyncio.Future()  # run forever
 
if __name__ == "__main__":
    asyncio.run(main())

Step 4. Create a sample py file for the client, and add the below code.

import websockets
import asyncio
 
# The main function that will handle connection and communication
# with the server
async def ws_client():
    print("WebSocket: Client Connected.")
    url = "ws://127.0.0.1:7890"
    # Connect to the server
    async with websockets.connect(url) as ws:
        while True:
            endpoint_with_input = input("Type endpoint param1 param2 so on ")
    
            if endpoint_with_input == 'exit':
                exit()
            
            # Send values to the server
            await ws.send(f"{endpoint_with_input}")
            # Stay alive forever, listen to incoming msgs
        
            print("===============================")
            msg = await ws.recv()
            print(msg)
            print("================================")
 
# Start the connection
asyncio.run(ws_client())

Step 5. In one terminal run the server application.

Server started

Step 6. In another terminal run the client application.

Client connected

Step 7. Below is the snap of the executed code.

Executed code

Summary

I hope it helps to create and understand WebSocket communication.