"thin clients" communicating with ROS

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Rosbridge is a perfect solution. You can write a client that connects to rosbridge using any language that has a websocket library. Websocket is a poor choice of name for the protocol because it implies use by web browsers only. Sure, it was designed for web browsers, but the protocol itself is just a layer on top of TCP and provides a number of useful properties.

As for the rosbridge ROS node - we have just released rosbridge v2.0 beta, which is the 'industrial strength' rosbridge. It has a much more robust server implementation and a more well defined protocol. We haven't yet officially released v2.0 on ROS.org so the information on the ROS wiki is still for v1.0. The most up to date resource is rosbridge.org (for both v1.0 and v2.0 of rosbridge). The source code repository for v2.0 is here.

To give you the gist of how rosbridge works, you can check out some example rosbridge commands on this page.

To actually write a client that connects to rosbridge, all you need is a websockets library. For example, the following python client connects and calls a ROS service. In the example we use the ws4py websocket client library.

from json import dumps
from ws4py.client.threadedclient import WebSocketClient

class GetLoggersClient(WebSocketClient):

     def get_loggers(self):
         msg = {'op': 'call_service', 'service': '/rosout/get_loggers'}
         self.send(dumps(msg))

     def opened(self):
         print "Connection opened..."
         self.get_loggers()

     def closed(self, code, reason=None):
         print code, reason

     def received_message(self, m):
         print "received", m

if __name__=="__main__":
     try:
         ws = GetLoggersClient('ws://127.0.0.1:9090/')
         ws.connect()
     except KeyboardInterrupt:
         ws.close()