On upgrade websockets how can to send additional headers?

[polearnik]

I Try next code but upgrade is not sended

upgrade: (res, req, context) => {
    console.log('An Http connection wants to become WebSocket, URL: ' + req.getUrl() + '!');
res.writeHeader('Test',123)
    /* This immediately calls open handler, you must not use res after this call */
    res.upgrade({
        url: req.getUrl()
      },
      /* Spell these correctly */
      req.getHeader('sec-websocket-key'),
      req.getHeader('sec-websocket-protocol'),
      req.getHeader('sec-websocket-extensions'),
      context);

  },

[e3dio]

Add res.writeStatus('101') before adding any headers in upgrade handler, see https://github.com/uNetworking/uWebSockets.js/discussions/331 Also you are writing a number 123 instead of a string, need a string