ROS - rosbridge - PLC

[Felix Messmer]

Hi everyone,

I am using rosbridge_v1 for communication between ROS and....

.... wait for it ....

... a Siemens PLC to use ROS navigation with an AGV.

Now I found out that there is a rosbridge_v2, so I joined this group and read the specification to find out whether I should switch to rosbridge_v2 as well.
Unfortunately, we are using raw socket communication between the PLC and rosbridge.

So since rosbridge_v2 does not support TCP/IP socket (yet), we'll stick to rosbridge_v1 for the time being.

I just wanted to let you know about this "misuse" of rosbridge (since it is intended to communicate with browsers ;-)
Also, this post is just to point out interest in rosbridge_v2 supporting TCP/IPC sockets (again) as well.
The protocol looks very nice and much simpler - good job!

So maybe in the next step for the AGV we can help adding TCP/IP support to rosbridge_v2.
We also already discussed, whether it is possible to support other industrial protocols such as ProfiNET.


With best regards,
Felix

[Chad Jenkins]

Hi Felix,

Oh yeah!  That is what rosbridge is all about.  Very cool.  Please feel free to share more (code, pics, videos) if you are so inclined.

First, rosbridge is not intended only for use with browsers.  rosbridge is meant to be a general network protocol for robotics to support communication between robot applications and robot systems/middleware.  The design of rosbridge was aimed to cover cases ignored by the traditional ROS environment: embedded systems [*], integration with existing non-ROS code, and (eventually) closed source industrial implementations of ROS as well as web interfaces.  Sorry I am overreacting, but this is a common misconception  :(

[*] http://brown-robotics.org/wp/rosbridgearduino-video-tutorial/

---

Thanks for the kind words about v2  :)

Jon Mace and I had several discussions about whether to include TCP/IP sockets along with websockets for v2.  Jon had convincing arguments to just stick with websockets for now:

  1) rosbridge v1 tried to detect when an incoming connection was a raw socket or a websocket, causing additional (unnecessary) complexity for the server.  The v2 design assumes a rosbridge port can be open with either form of socket, but not both.
  2) rosbridge_library (in v2) can be wrapped to use a raw socket.  The default v2 server essentially wraps around this library
  3) Jon posited that creating a raw socket version of rosbridge v2 would be "trivial".  As indicated in your message, we would welcome your addition of a TCP/IP socket version of the v2 server to the stack

We would also welcome any contributions for supporting rosbridge over other transports. 

Thanks!
-Chad

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