Support different client and server ports

This is related to https://github.com/lydell/elm-watch/issues/39 which solved my problem for SSL hand off being done by an external server (An nginx Ingress in Kubernetes in this case).

I was able to have elm-watch listening on port 443 (but serving HTTP not HTTPS) as this port was not being used by anything else as the nginx was running elsewhere.

However, in another use case I have, I am running everything on my laptop - I use a local haproxy to do the SSL handoff. This of course must listen on port 443 thus not allowing elm-watch to also listen on this port.

Therefore I would really like to be able to configure the elm-watch client port to be 443 but set the server port to something else. In haproxy I would then rewrite /elm-watch to the server port.

I know that you are not keen on extra configuration options, so perhaps this could be done via an environment variable either to change the client port or the server port?

[chazsconi]

For now, you can use a hack like this:

<script>
window.WebSocket = class HackWebSocket extends WebSocket {
  constructor(urlParam) {
    const url = new URL(urlParam);
    if (looksLikeElmWatch(url)) {
      url.port = "1234";
    }
    super(url);
  }
}

function looksLikeElmWatch(url) {
  return url.port === "4321";
  // or return url.pathname === "/elm-watch";
}
</script>

This works great - thanks for the tip!

Ok, one more question: If I were to add cert configuration to elm-watch.json, would it look something like this for you then?

{
  "sslCertificate": {
    "cert": "./ssl/le-certs/foo.crt",
    "key": "./ssl/le-certs/foo.key"
  },
  "targets": {}
}

Yes, this would be perfect.

So far, I’ve only found HAProxy that concatenates them. And even in that case, couldn’t you “just” keep three files on disk?

In fact HAProxy doesn’t concatenate them - it just expects all the files in the same folder.

[chazsconi]

Just some extra info for anyone else using a setup with HAProxy: To prevent elm-watch from frequently reloading, you will need to add something like this to your HAProxy config in the backend section for elm-watch

timeout tunnel 1h