Hi!

We've been working on our comm node and we have encountered a problem.

We are thinking about creating a ROS msg that looks like this:

int robot_id
ShapeShifter msg

2010/7/9 Gonçalo Cabrita <goncabrita@gmail.com>

> Hum... I'm not sure that will do the trick :)
>
> What Pedro is aiming for is a ROS node where robots can dynamically connect
> to each other. He is using multi-cast so that newcomers can tell other
> robots that they are there and ready to communicate, so the new IP address
> is added to the table of addresses of each robot. From there each robot
> should be able to open a foreign_relay to any robot on the list.
>
> The idea is that we don't need a list of robots or IPs in advance. Robots
> can join and leave the network as necessary, in a p2p fashion.
>
> I believe Pedro's problems are related to multi-threading and how to
> exactly tweak the foreign_relay node in order to accomplish this goal,
> however he is more qualified to elaborate on the exact problems he has
> encountered :)
>
> Another option (I think!) would be to have the multi-cast thingie on a node
> which would open and close the foreign_relay nodes from within the code as
> needed, as opposite to running the foreign_relay code from within the same
> node in multiple threads.
>
> Is there a way to accomplish this last idea?
>
> Gonçalo Cabrita
> ISR - University of Coimbra
> Portugal
>
> On Jul 8, 2010, at 11:06 PM, Blaise Gassend wrote:
>
> > You can launch any number of foreign relays from a launch file. Here is
> > a line from one launch file I was working with:
> >
> > <node name="trigger_foreign_relay" pkg="foreign_relay"
> type="foreign_relay.py" args="sub /trigger $(env FOREIGN_MASTER)"
> respawn="true"/>
> >
> > If I recall, I had to tweak foreign_relay to make this work. The foreign
> relay here should do the trick:
> >
> https://code.ros.org/svn/wg-ros-pkg/trunk/stacks/dance_demo/foreign_relay
> >
> > On Thu, 2010-07-08 at 15:56 +0100, Pedro Sousa wrote:
> >> Hello everyone
> >>
> >>
> >> I am working with Gonçalo with ROS and our mobile platform (Roombas
> >> and Eeepc on top) and I am following this conversation about
> >> multi-robot communication. Like Blaise said the foreign_relay_node was
> >> a great way of sharing information between robots. However, this
> >> approach is good when the initialisation of the node is made directly
> >> on the console or giving the parameters inside the code.
> >>
> >>
> >> I was trying to go a bit further and make it for multi robot. However,
> >> it wasn't easy for me and with some "bad hacks" I was able to
> >> advertise a certain node of one robot on others (two) robots.
> >>
> >>
> >> Anyone have already made something similar? If not, how is the correct
> >> way of doing so?
> >>
> >>
> >>
> >>
> >> Regards,
> >>
> >>
> >> Pedro Sousa
> >> ISR - University of Coimbra
> >> Portugal
> >>
> >>
> >>
> >>
> >>
> >>
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> >
> >
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