Events aren't appearing in the browser

mark-hahn commented 8 years ago

I'm having problems getting events to come through. I think I have everything set up (but I am often wrong).

getConnectionCount shows one connection
I'm definitely calling send
The chrome dev inspector shows the connect event as expected
I'm pretty sure my events are set up correctly in the browser since the open event works.
I have all events registered including error so I'm confident there is no error
I have a setInterval in both the browser and server showing good status repeatedly

Server code ...

channel = new SseChannel
  historySize: 10
  retryTimeout: 250
  pingInterval: 5000
  jsonEncode: yes

--- snip ---

  when '/channel'
    res.setHeader 'Transfer-Encoding', 'identity'
    channel.addClient req, res, (err) ->
      if err then log 'channel.addClient err:', err.message

--- snip ---
do sendStatus = ->
  vlc.status (err, status) ->
    if err then log 'sendStatus err: ', err
    else
      log 'channel.send', channel.getConnectionCount(), status
      channel.send 
        event: 'status'
        id:     Date.now()
        data:   status
        retry:  5000
    setTimeout sendStatus, 2000

Client code ...

    evtSource = new EventSource "http://#{tvGlobal.serverIp}:2340/channel"
    log 'evtSource', evtSource

    evtSource.onopen = (e) ->
      log 'evtSource.onopen1:', e

    evtSource.onmessage = (e) ->
      log 'evtSource.onmessage:', e

    evtSource.onerror = (e) ->
      log 'evtSource.error:', e

    evtSource.addEventListener 'open', (e) ->
      log 'evtSource.onopen2:', e

    evtSource.addEventListener 'message', (e) ->
      log 'evtSource.onmessage:', e

    evtSource.addEventListener 'error', (e) ->
      log 'evtSource.error:', e

    setInterval ->
      log 'evtSource', evtSource
    , 5000

If you can't think of any easier way to debug I'll try capturing packets.

Ubuntu 14.04 node 0.12.9 sse-channel 2.0.0 chrome 47.0.2526.106

rexxars commented 8 years ago

Couple of things:

Bit curious as to why you're explicitly setting transfer-encoding to identity? SSE should use chunked (and sse-channel sends that header automatically, iirc)
You're sending messages with event type status, but you are listening to the message event. Instead, hook up an event listener on status. Eg: evtSource.addEventListener('status', function(e) { /* ... */ });

If you're still having trouble getting it to work, try using curl and checking that messages are actually being broadcasted: curl http://localhost:2340/channel

mark-hahn commented 8 years ago

hook up an event listener on status

That fixed it. Thanks very much. Maybe this should be in the readme. Maybe a short section on what to do in the browser. The readme currently assumes the user knows SSE in advance. I stupidly looked for a module to run in the browser until I found out it wasn't needed. If I get a chance I'll do a PR.

SSE should use chunked

Chrome threw an error saying chunked can't be used. I also googled it and found that chunked is considered a relibility problem.

"Authors are also cautioned that HTTP chunking can have unexpected negative effects on the reliability of this protocol. Where possible, chunking should be disabled for serving event streams unless the rate of messages is high enough for this not to matter." From https://html.spec.whatwg.org/multipage/comms.html#authoring-notes

Edit: Weird. I commented out the identity header and had no problem. Apparently that error was triggered by my problem, which makes no sense. I didn't imagine the error.

Thanks again for the fast response.

rexxars commented 8 years ago

Thanks for the feedback on the transfer-encoding, learn something new every day :-)

I'll see if I can find the time to make a few notes in the readme about browser usage.

rexxars commented 8 years ago

Thanks again for the feedback. I've added some client usage notes to the readme: https://github.com/rexxars/sse-channel/commit/6d6f2cac8590b9aedec763d7afdaa97c12ee7379

rexxars / sse-channel

Events aren't appearing in the browser #8