Trouble to get MQTT JavaScript Client running

Question

I try to get a MQTT JavaScript Client running. It's based on the Eclipse Paho Client Library (org.eclipse.paho.mqtt.javascript.git).

Before running the JavaScript Client I was performing some tests with

mosquitto_pub -h test.mosquitto.org -t "/topic1" -m "test"

and

mosquitto_sub -h test.mosquitto.org -t "/topic1" -v

which are working fine.

Then I called my own mqttTest.html which contains:

<!DOCTYPE html>
<head>

  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">  
  <script type="text/JavaScript" src="mqttws31.js"></script>
  <script type="text/JavaScript">

  var client;

  function doConnect() {

    client = new Messaging.Client("test.mosquitto.org", 1883, "mosqOtti");
    console.log("Client instantiated.");
    client.startTrace();
    console.log("Now trying to connect...");
    client.connect({onSuccess:onConnect});

  }

  function onConnect() {

    console.log("connection established");
    doSubscribe();

  }

  function doSubscribe() {

      client.subscribe("/topic1");

  }

  window.onload = function() {

      this.doConnect();

  }

</script>
</head> 

.
.
.

</body>
</html>

I tried to lauch this in Firefox. The debug console output tells me that

[09:58:27.825] Firefox can't establish a connection to the server at ws://test.mosquitto.org:1883/mqtt. @ file:///mqttws31.js:914

I know that moquitto does not support websockets natively. But I red that the lighttp running on test.mosquitto.org has mod_websockets installed.

Line 914 of mqttws31.js is trying to do this.socket = new WebSocket(wsurl, 'mqttv3.1');

So it seems that

either websockets doesn't really work for test.mosquitto.org
or my example is buggy!

I stuggled around for a long time now and need to get a JavaScript MQTT Client running.

Does anyone have an idea? Or another approach? Socket.IO seems not to be the right solution too.

Thanks very much in advance!

I think the problem is that the websocket support on test.mosquitto.org does not share the same port (1883) as the normal mqtt broker. This is because the websocket support uses lighttpd to front for mosquitto. Hopefully Roger can remind us what port is needed. — hardillb
– hardillb, Commented Sep 9, 2013 at 9:06

ralight · Accepted Answer · 2013-09-09 13:19:59Z

5

As @hardillb says, the port you are using is incorrect. 1883 on test.mosquitto.org is solely for mqtt. If you wish to use websockets you need to connect using port 80. You should just be able to change your url to ws://test.mosquitto.org:1883/mqtt which presumably means changing your code to

client = new Messaging.Client("test.mosquitto.org", 80, "mosqOtti");

There is a websockets example (based on this code) running at http://test.mosquitto.org/sys/. Although it uses the deprecated mosquitto javascript client, it should demonstrate that it works.

The lighttpd config on test.mosquitto.org is:

websocket.server = (
    "/mqtt" =>
    (  
        "host" => "127.0.0.1",
        "port" => "1883",
        "subproto" => "mqttv3.1",
        "type" => "bin"
    )
)

edited Sep 9, 2013 at 13:19

answered Sep 9, 2013 at 9:47

ralight

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2 Comments

marrrschine Over a year ago

okay great hint, thank you! it works! i just installed the mod_websockets for my own lighttpd. If i configure the stuff according to github.com/nori0428/mod_websocket/blob/master/INSTALL, I tried to change the example, that is: websocket.server = ("/mqtt" => ( "host" => "127.0.0.1", "port" => "1883" ), where on port 1883 i have moquitto running and listening, and now trying to connect via client = new Messaging.Client("localipaddr", 80, "mosqOtti");

ralight Over a year ago

I've added the lighttpd config I use to the answer.

garromark · Accepted Answer · 2014-03-01 01:18:53Z

I had a lot of trouble getting this to work for me and wanted to post solution for Ubuntu that was quickest/easiest for me.

To install lighttpd with websocket support on Ubuntu

Basically, follow this blog post: http://oriolrius.cat/blog/tag/mqtt/

Steps:

1) Add repository for your version of ubuntu from here: https://launchpad.net/~roger.light/+archive/ppa/

For Ubuntu 12.04 LTS (Precise), the lines are:

deb http://ppa.launchpad.net/roger.light/ppa/ubuntu precise main
deb-src http://ppa.launchpad.net/roger.light/ppa/ubuntu precise main

2) Install lighttpd and mod_websocket plugin:

apt-get update
apt-get install lighttpd lighttpd-mod-websocket

3) Add configuration for MQTT websocket somewhere that's included by /etc/lighttpd/lighttpd.conf

server.modules = ( "mod_websocket", )

websocket.server = (
    "/mqtt" => (
        "host" => "127.0.0.1",
        "port" => "1883",
        "type" => "bin",
        "subproto" => "mqttv3.1"
    ),
)

...

4) Optionally, point lighttpd at non-html socket. This worked

server.port = 8080

5) Restart lighttpd, and Javascript client connects to http://hostname:8080. I used Paho Javascript client following commands represented here: https://www.ibm.com/developerworks/community/blogs/c565c720-fe84-4f63-873f-607d87787327/entry/how_to_prog_javascript?lang=en

service lighttpd restart

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