WebSocket

Compatibility	CPython & MicroPython
Required Microdot source files	websocket.py helpers.py
Required external dependencies	None
Examples	echo.py

The WebSocket extension gives the application the ability to handle WebSocket requests. The with_websocket decorator is used to mark a route handler as a WebSocket handler. Decorated routes receive a WebSocket object as a second argument. The WebSocket object provides send() and receive() asynchronous methods to send and receive messages respectively.

Example:

from microdot.websocket import with_websocket

@app.route('/echo')
@with_websocket
async def echo(request, ws):
    while True:
        message = await ws.receive()
        await ws.send(message)

To end the WebSocket connection, the route handler can exit, without returning anything:

@app.route('/echo')
@with_websocket
async def echo(request, ws):
    while True:
        message = await ws.receive()
        if message == 'exit':
            break
        await ws.send(message)
    await ws.send('goodbye')

If the client ends the WebSocket connection from their side, the route function is cancelled. The route function can catch the CancelledError exception from asyncio to perform cleanup tasks:

@app.route('/echo')
@with_websocket
async def echo(request, ws):
    try:
        while True:
            message = await ws.receive()
            await ws.send(message)
    except asyncio.CancelledError:
        print('Client disconnected!')