Proxy for websocket without the context does not work.

[garnesen]

Proxying works fine when I use

const app = express();
const proxy = require('http-proxy-middleware');
const wsProxy = proxy('/socket.io', {target:'ws://my-websocket.com/', changeOrigin: true, ws:true});
app.use(wsProxy);

but it does not work if I use

const app = express();
const proxy = require('http-proxy-middleware');
app.use('/socket.io', proxy({target:'ws://my-websocket/', changeOrigin: true, ws:true}));

Am I doing this wrong, or is this a bug?

[garnesen]

Looks similar to this issue #204

[garnesen]

After doing some research, it seems with the not working example, express never hits the middleware function at

http-proxy-middleware/lib/index.js

Line 38 in bb59c66

function middleware (req, res, next) {

This means catchUpgradeRequest is never called and therefore no handler is set for upgrade and the proxy is never made. In the first working example, the middleware is called for all requests so the upgrade handler is set.

Why express middleware not working for /socket.io? I do not know..

[garnesen]

I tried using plain Websockets in case it was a socket.io problem and it looks like express middleware does not seem to catch any of it. I saw there are libraries to add middleware for websockets but it seems like a solution to my problem is to not use middleware at all. I can simply do

const app = express();
const proxy = require('http-proxy-middleware');
const wsProxy = proxy('/socket.io', {target:'ws://my-websocket.com/', changeOrigin: true, ws:true});
const server = app.listen(...);
server.on('upgrade', wsProxy.upgrade);

[sincerefly]

@garnesen

Add app.use(wsProxy); and it's works well, thanks

[maitrungduc1410]

thank you, it's weird :D