Ten-Minute Guide to rosbridge

More information is available from: 
http://ros.org/wiki/rosbridge (the documentation page for rosbridge on ros.org)
http://ros.org/wiki/rosjs (the ros.js documentation page)
and by writing tjay@cs.brown.edu

After installing ROS ( http://www.ros.org/wiki/ROS/Installation ), rosbridge is available either:

1) By apt-get repository (after installing the ROS apt sources) via:
sudo apt-get install ros-electric-brown-remotelab

or 

2) Via SVN checkout:
svn co https://brown-ros-pkg.googlecode.com/svn/trunk/experimental/rosbridge rosbridge

to launch rosbridge:
rosrun rosbridge rosbridge.py

by default rosbridge runs on port 9090 .

To talk to rosbridge, use JSON ( http://www.json.org/ ) messages wrapped in byte 0 and byte 255 (you may optionally include a newline before the 255. Communication from the server will come similarly wrapped, and with a newline before the 255. rosbridge only supports pure ASCII messages.

To publish:
{"receiver":"/topic","msg":{"fieldname":"value"},"type":"ros/type"}

To make a service call:
{"receiver":"/service","msg":["in","order","arguments"]}

Most of the functionality of the ROS C++ and Python API is available as pseudo-services provided by rosbridge. See the ros.js tutorial for more information.

Example:
{"receiver":"/rosbridge/subscribe","msg":["/topic",-1,"type"]}

subscribes to the /topic regardless of whether it currently exists.