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Adjust Websocket-over-HTTP example to work out of the box #35

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Adjust Websocket-over-HTTP example to work out of the box #35

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54596bb
Adjust Websocket-over-HTTP example to work out of the box
viktorvsk Feb 5, 2024
aae407d
Add descriptive comment to an example
viktorvsk Feb 5, 2024
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40 changes: 30 additions & 10 deletions samples/websocket-over-http.js
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,12 @@ const {
Publisher,
} = require('@fanoutio/grip');

const PUBLISHER = new Publisher({
'control_uri': 'http://localhost:5561',
});

const CHANNEL = 'all';

http.createServer(async (req, res) => {
// Validate the Grip-Sig header:
if (!validateSig(req.headers['grip-sig'], 'changeme')) {
Expand All @@ -27,6 +33,15 @@ http.createServer(async (req, res) => {
return;
}

let responseBody;

// Manually set headers to accept Websocket-over-HTTP
res.setHeader('Content-Type', 'application/websocket-events');
res.setHeader('Sec-WebSocket-Extensions', 'grip');

// This header causes issues with Node v20.8.1 — wscat hangs and disconnects in 5 seconds
res.removeHeader("Transfer-Encoding");

const inEventsEncoded = await new Promise(resolve => {
let body = '';
req.on('data', function (chunk) {
Expand All @@ -43,30 +58,35 @@ http.createServer(async (req, res) => {
if (wsContext.isOpening()) {
// Open the WebSocket and subscribe it to a channel:
wsContext.accept();
wsContext.subscribe('<channel>');

// This adds a control messsage to output that goes to client (?)
wsContext.subscribe(CHANNEL);
// It doesn't work without it
res.setHeader('Grip-Channel', CHANNEL);

// The above commands made to the wsContext are buffered
// in the wsContext as "outgoing events".
// Obtain them and write them to the response.
const outEvents = wsContext.getOutgoingEvents();
const outEventsEncoded = encodeWebSocketEvents(outEvents);
res.write(outEventsEncoded);
responseBody = outEventsEncoded;

// As an example way to check our subscription, wait and then
// publish a message to the subscribed channel:
setTimeout(() => {
var publisher = new Publisher({
'control_uri': '<myendpoint>',
});
publisher.publishFormats(
'<channel>',
new WebSocketMessageFormat('Test WebSocket Publish!!')
);
PUBLISHER.publishFormats(CHANNEL, new WebSocketMessageFormat('Test WebSocket Publish!!'));
}, 5000);
} else {
// Here we emulate some sort of echoing to demonstrate
// how an origin could react to incoming websocket messages
const [command, payload] = inEventsEncoded.split("\n").map(s => s.trim());
const messageToClient = JSON.stringify({command, payload});
PUBLISHER.publishFormats(CHANNEL, new WebSocketMessageFormat(messageToClient));
}

// Set the headers required by the GRIP proxy:
res.writeHead(200, wsContext.toHeaders());
res.writeHead(200);
if (responseBody) { res.write(responseBody) };
res.end();

}).listen(80, '0.0.0.0');
Expand Down