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How to create a websocket module
DEPRECATED. The --websocket option and WebSocket modules were removed in v3.
If your app needs a bi-directional communication channel with the server then WebSockets are the way forward.
Remember: Websockets are not compatible with HTTP2 therefore will not work with the --http2 flag.
This is the minimum code required to create a WebSocket server. Only the websocket method is required which receives a WebSocket.Server instance. This method is not required to return a value.
module.exports = SocketBase => class Socket extends SocketBase {
websocket (wss) {}
}To handle incoming WebSocket connections, attach a listener to the connection event. Save the following trivial echo server example in a file named ws-example.js:
module.exports = SocketBase => class Socket extends SocketBase {
websocket (wss) {
wss.on('connection', (ws, req) => {
ws.on('message', data => {
ws.send(`message received: ${data.toString()}`)
})
})
}
}Save the following client example to a file named index.html.
<!DOCTYPE html>
<html>
<head>
<title>WebSocket example</title>
</head>
<body>
<script>
const socket = new WebSocket('ws://127.0.0.1:8000/')
socket.onopen = function () {
socket.send('Trivial example')
}
</script>
</body>
</html>Now, launch ws with your WebSocket server and navigate to one of the listed URLs. You will be able to see socket communications in the DevTools Network panel.
$ ws --websocket ws-example.js
Serving at http://mbp.local:8000, http://127.0.0.1:8000, http://192.168.0.100:8000
You can set the options the Websocket.Server is created with by returning a plain object from the wsOptions method.
In this example, the WebSocket will only accept connections from requests to /socket.
module.exports = SocketBase => class Socket extends SocketBase {
wsOptions () {
return { path: '/socket' }
}
websocket (wss) {
wss.on('connection', (ws, req) => {
ws.on('message', data => {
ws.send(`message received: ${data.toString()}`)
})
})
}
}To send debug information to the --verbose output, you can emit a verbose event from any method within the module passing a key and value.
module.exports = MiddlewareBase => class Example extends MiddlewareBase {
middleware (options) {
return (ctx, next) => {
this.emit('verbose', 'middleware.example.config', { message })
ctx.response.body = options.message
}
}
}