mdonoughe / rosbridge

a ROS node for connecting JavaScript applications by WebSocket
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This is a very modified version of rosbridge from brown_remotelab.

See the wiki for documentation.

Changes

I've changed services to have callbacks like this:

{receiver: '/test_service', callback: 0, msg: {data: 'request'}}
{callback: 0, msg: {data: 'response'}}

so that you can have multiple requests in flight to the same service at the same time with different callbacks. This doesn't change the appearance of the JavaScript API, but it does change its behavior to work like you'd expect. As a result, the following code now prints 1 and 2 rather than 2 and 2.

connection.callService('/rosjs/subscribe', {
  data: ['/test1', 0],
  success: function(rsp) {
    console.log('1');
  }
});
connection.callService('/rosjs/subscribe', {
  data: ['/test2', 0],
  success: function(rsp) {
    console.log('2');
  }
});

It is also possible for an error to be returned from a service call. The following code prints "Topic does not exist" unless /unpublishedTopic is actually published.

connection.callService('/rosjs/subscribe', {
  data: ['/unpublishedTopic', 0],
  success: function(rsp) {
    console.log('success');
  },
  error: function(rsp) {
    console.log(rsp);
  }
});

The JavaScript API has changed. The event handlers are now just fields without setters, and there is no event handler for onerror because that's not part of the WebSocket spec.

You can also pass an extra argument to addHandler and callService, which will be passed as a second argument to your callback function.

// print 'hello' to the console every time a message comes in on /test
connection.addHandler('/test', function(msg, data) {
  console.write(data);
}, {arguments: ['hello']});

I was having an issue with terribleWSS using 100% CPU on my test machine, so I replaced it with txWebSocket and Twisted. txWebSocket is included in the bin directory, but Twisted must be installed manually. python-twisted from Debian works fine.

Note: the included txWebSocket is a slightly modified version from https://github.com/mdonoughe/txWebSocket .

Setting wspath changes the path to the websocket. By default, the path is '/', so you'd connect with 'ws://localhost:9090/'.

You'll probably want to change wspath if you set docroot, which causes a folder to be exposed at 'http://localhost:9090/'.

You can use jsfile(default is 'ros.js') to make the ros.js file visible at 'http://localhost:9090/ros.js', or set it to '' to make it disappear.

Parameters are now referenced as ~param instead of /brown/rosbridge/param. This means that you can easily set params in roslaunch like you'd expect.

Example

I'm using the following configuration with roslaunch to host a web application at http://0.0.0.0:9090/:

<node pkg="rosbridge" type="rosbridge.py" name="bridge">
  <param name="wspath" value="/ws"/>
  <param name="docroot" value="$(find aslam_input)/docroot"/>
</node>

A file index.html in the aslam_input/docroot includes /ros.js(automatically provided by rosbridge, not actually present in the docroot folder) and another script which uses new ros.Connection('ws://' + location.host + '/ws'); to connect to the websocket without hardcoding an address.