Proxying websockets to multiple backends doesn't work

Is this a bug report?

Yes

Steps to reproduce

1. Set up a proxy server with

app.use(
  '/sockjs-node',
  createProxyMiddleware('/sockjs-node', {
    target: 'http://127.0.0.1:3000',
    ws: true,
  })
);
app.use(
  '/socket.io',
  createProxyMiddleware('/socket.io', {
    target: 'http://127.0.0.1:4000',
    ws: true,
  })
);

The /sockjs-node server can be quickly spun up with create-react-app since that is the socket for Webpack hot reload. /socket.io can be quickly spun up with a socket.io example server.

1. Load up the React app in your browser. The /sockjs-node requests are not proxied correctly. The HPM log output shows that it is trying to proxy the /sockjs-node request to port 4000, resulting in an ECONNREFUSED error.

Setup

• http-proxy-middleware: 1.0.5
• http-proxy-middleware configuration: see above
• server: express 4.17.1

client info

Chrome (latest) / Ubuntu 20.04 (Linux)

target server info

One is a webpack dev server, one is a simple express server with socket.io config

Reproducible Demo

https://github.com/bduffany/hpm-bug

[bduffany]

I found that if I change

app.use(
  '/sockjs-node',
  createProxyMiddleware('/sockjs-node', {
    target: 'http://127.0.0.1:3000',
    ws: true,
  })
);

to

app.use(
  createProxyMiddleware('/sockjs-node', {
    target: 'http://127.0.0.1:3000',
    ws: true,
  })
);

Then the issue is fixed. No ideas yet as to why. However, I think this fix results in worse performance, because express is now going to be running that proxy middleware on every request, even ones that don’t match /sockjs-node. It might be OK though if you’re only using this for local development.

[Cheyenne55]

You just saved my day with your fix. Spent 3 hours because I had this exact problem.

When proxying to several websocket servers Chrome was showing errors like “Invalid frame header” or “WebSocket connection failed: One or more reserved bits are on: reserved1 = 0, reserved2 = 1, reserved3 = 1” which googling them up led to absolute non-sense.

I think this issue should really be patched up.