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rosbridge_server: share messages to non-ROS computer using HTTP

asked 2015-07-29 19:26:05 -0500

frankb gravatar image

Is there a way to share a topic with a non-ROS computer? I am trying to send a string from my ros computer to another computer over a local static ip network. I was looking into using rosbridge_server to do this as it claims "Rosbridge provides a JSON API to ROS functionality for non-ROS programs."

I followed the tutorial: http://wiki.ros.org/rosbridge_suite/T... and used roslibjs as indicated here: http://wiki.ros.org/roslibjs/Tutorial...

While testing solely on my ros computer, I was able to subscribe to my topic over a websocket and have the string displayed on the web console using this HTML code:

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />

<script type="text/javascript" src="http://cdn.robotwebtools.org/EventEmitter2/current/eventemitter2.min.js"></script>
<script type="text/javascript" src="http://cdn.robotwebtools.org/roslibjs/current/roslib.min.js"></script>

<script type="text/javascript" type="text/javascript">
  // Connecting to ROS
  // -----------------

  var ros = new ROSLIB.Ros({
    url : 'ws://localhost:9090'
  });

  ros.on('connection', function() {
    console.log('Connected to websocket server.');
  });

  ros.on('error', function(error) {
    console.log('Error connecting to websocket server: ', error);
  });

  ros.on('close', function() {
    console.log('Connection to websocket server closed.');
  });

  // Subscribing to a Topic
  // ----------------------

  var listener = new ROSLIB.Topic({
    ros : ros,
    name : '/copter_center_str',
    messageType : 'std_msgs/String'
  });

  listener.subscribe(function(message) {
    console.log('Received message on ' + listener.name + ': ' + message.data);
    //listener.unsubscribe();
  });

</script>
</head>

<body>
  <h1>Simple roslib Example</h1>
  <p>Check your Web Console for output.</p>
</body>
</html>

However, this method requires a web connection to include eventemitter2 and roslib. I tried installing both libraries and writing a javascript file to do it offline, but did not work as there were issues installing roslib.

It seems like roslib is designed to be used as a web interface to access ROS topics and services. Can rosbridge be used to give another computer access to a single topic and its messages over a local offline connection? If not, how is this interaction typically done? It would be perfect if there existed an HTTP call to subscribe to a topic on the rosbridge server.

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answered 2015-07-30 09:18:33 -0500

rtoris288 gravatar image

rosbridge is simply a protocol specification for external clients to communicate with ROS ( https://github.com/RobotWebTools/rosb... ). By running rosbridge server, you are allowing any external client to connect to a ROS system via either a WebSocket or TCP connection (depending on which server you start). roslibjs is a JavaScript client library; however it is not the only option. A Java implementation also exists ( https://github.com/WPI-RAIL/jrosbridge/ ) any other languages can also implement the protocol and become a client as well.

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Asked: 2015-07-29 19:26:05 -0500

Seen: 747 times

Last updated: Jul 30 '15