How To Use Python To Create WebSocket Server & Client Example

This article will tell you how to use Python to develop a WebSocket server and client applications with examples. It will use the python websockets module and asyncio module.

1. Install The Python websockets Module.

1. Open a terminal and run the command pip show websockets to see whether the Python websockets module has been installed or not.

   (MyPythonEnv) C:\Users\zhaosong>pip show websockets 
   WARNING: Package(s) not found: websockets

2. If it shows can not find the websockets module, then you can install it with the command pip install websockets.

   (MyPythonEnv) C:\Users\zhaosong>pip install websockets
   Collecting websockets
     Downloading websockets-10.3-cp38-cp38-win_amd64.whl (98 kB)
        |████████████████████████████████| 98 kB 1.3 MB/s
   Installing collected packages: websockets
   Successfully installed websockets-10.3

3. Run the command pip show websockets again to verify that the websockets module has been installed successfully.

   (MyPythonEnv) C:\Users\zhaosong>pip show websockets
   Name: websockets
   Version: 10.3
   Summary: An implementation of the WebSocket Protocol (RFC 6455 & 7692)
   Home-page: https://github.com/aaugustin/websockets
   Author: Aymeric Augustin
   Author-email: aymeric.augustin@m4x.org
   License: BSD
   Location: c:\users\zhaosong\anaconda3\envs\mypythonenv\lib\site-packages
   Requires:
   Required-by:

2. Python Client & Server WebSockets Example.

2.1 Create WebSockets Server.

1. Before you can use the Python websockets module you should first import it.

   import websockets

2. Define an async function as the handler that will handle the client websocket request. In this function, you can receive client request data using the websocket.recv() method and then sent data back to the client on the server-side using the websocket.send(response_data) method. In this example, the function is async def websocket_request_handler(websocket, path).

   async def websocket_request_handler(websocket, path):
    
       # receive the client websocket send data.
       client_data = await websocket.recv()
    
       # construct the response data.
       response_data = "Below is the data recieved from client:\n" + client_data
    
       await websocket.send(response_data)

3. Call the websockets.serve(websocket_request_handler, host, port_number) method to start the WebSocket server and make it listen to the client websocket request.

   # create and start the websocket server listen on the provided host and port number.
   def start_websocket_server(host, port_number):
   
       # create the websocket server with the provided handler, host, and port_number.
       websocket_server = websockets.serve(websocket_request_handler, host, port_number)
    
       print('websocket server is running and listening on port number : ' + str(port_number))
   
       # run the websocket server asynchronouslly.
       asyncio.get_event_loop().run_until_complete(websocket_server)
       asyncio.get_event_loop().run_forever()

4. In this example, the websocket server is implemented in the file WebSocketsServer.py, below is the file source code.

   import websockets
   import asyncio
   import time
   
   # create handler for each connection
   # when there is a connection to the websocket server, the handler function will be invoked.
   # You can receive data from the client websocket and send data back to the client in this function. 
   async def websocket_request_handler(websocket, path):
    
       # receive the client websocket send data.
       client_data = await websocket.recv()
   
       print(time.ctime() + '\n' + client_data + '\n\r')
    
       # construct the response data.
       response_data = "Below is the data recieved from client:\n" + client_data
    
       # send the data back to the client websocket.
       await websocket.send(response_data)
    
   
   # create and start the websocket server listen on the provided host and port number.
   def start_websocket_server(host, port_number):
   
       # create the websocket server with the provided handler, host, and port_number.
       websocket_server = websockets.serve(websocket_request_handler, host, port_number)
    
       print('websocket server is running and listening on port number : ' + str(port_number))
   
       # run the websocket server asynchronouslly.
       asyncio.get_event_loop().run_until_complete(websocket_server)
       asyncio.get_event_loop().run_forever()
   
   
   if __name__ == '__main__':
   
       host = "localhost"
   
       port_number = 9999
   
       start_websocket_server(host, port_number) 
   

5. When you run the above python file with the command python .\WebSocketsServer.py, you will get the output like below. The text is the data sent from the client WebSocket, you will know it later.

   > python .\WebSocketsServer.py
   websocket server is running and listening on port number : 9999
   Fri May  6 18:51:59 2022
   hello
   how are you?
   I love python

2.2 Create WebSockets Client.

1. The example client websockets file name is WebSocketsClient.py, you can run it with the command python .\WebSocketsClient.py.

   > python .\WebSocketsClient.py
   Please input the text send to the websocket server, type send to finish.
   
   >hello
   >how are you?
   >I love python
   >send
   Below is the data recieved from client:
   hello
   how are you?
   I love python

2. Below is the WebSocketsClient.py source code.

   import asyncio
   import websockets
    
   # define the async function that send the text to the websocket server. 
   async def ping_websocket_server(send_text):
       
       # define the websocket server access URL.
       websocket_server_url = 'ws://localhost:9999/'
       
       # connect to the websocket server.
       async with websockets.connect(websocket_server_url) as websocket:
   
           # send the text to the websocket server and wait for the reply.
           await websocket.send(send_text)
   
           # get the websocket server return text.
           server_resp = await websocket.recv()
   
           # print out the server response text.
           print(server_resp)
   
   
   # this function will send the text to the websocket server by invoking the ping_websocket_server(send_text) function.  
   def create_websocket_client(send_text):
   
       # call the asyncio function to invoke the ping_websocket_server(send_text) function.
       asyncio.get_event_loop().run_until_complete(ping_websocket_server(send_text))
   
   
   
   if __name__ == '__main__':
   
       print('Please input the text send to the websocket server, type send to finish.\n\r')
   
       send_data_all = ''
       
       # loop to get the user input text to send.
       while True:
   
           input_data = input('>')
   
           # when user type 'send' then break the loop.
           if input_data.lower() == 'send':
   
               break
   
           send_data_all += input_data + '\n'
   
       
       create_websocket_client(send_data_all)