Hi Pedro et al, 

At Brown, we are solving the detection of new nodes/removal of nodes in the
network by using the BATMAN mesh networking protocol
(http://www.open-mesh.org/). With the BATMAN executable running on each
robot, all of the multicasting and routing are handled automagically. Then,
the robots can send messages to each other simply by using C++ sockets. 

We have a (very!) experimental ROS node that queries BATMAN to get the
neighbors of each robot and the corresponding link qualities available in
the Brown experimental ROS SVN repository: 
svn checkout
http://brown-ros-pkg.googlecode.com/svn/trunk/experimental/meshnet/batman_mesh_info


Regarding handling the messages sent among the robots, for now we have
custom C++ code to send ROS topics (serialized into byte arrays) that are
specific to our application. Moving towards a more general solution, using
foreign_relay for message passing sounds like an interesting alternative.
Please elaborate a bit more on the exact problems you have encountered. 

Best,

Aggeliki Tsoli
Brown University
USA