best practices for intermittent connectivity

In the JXTA application I am developing I have many peers which are 
sending data to a smaller number of remote peers.  For any number of 
reasons it is always possible that a remote peer will become 
unreachable.  When a remote peer is unreachable the local peer should 
find another peer that is reachable providing the same service, and 
continue operation.

My question is:

Can somebody provide me with an example of how to discover that the 
remote endpoint on a unicast pipe has become unreachable, and recover 
from this?  I see from the documentation that OutputPipe.send() returns 
a boolean that, if false, usually indicates there is congestion and the 
peer should try again later.  How long should I wait?  Should I 
implement an exponential backoff algorithm?  How many times should I 
retry before giving up?  Is this actually a rare event that I don't 
need to expend much effort on?  I can experiment, but I am hoping to 
find some suggestions.

Also, I see that OutputPipe.send() can throw IOException.  When this is 
thrown does it always mean the remote peer has become unreachable, or 
can it indicate other problems?  If I catch this exception, should I 
close the pipe and try to open it again, and find another peer only if 
that fails?  Or can I assume this means peer is gone?  Or should I use 
some other means to probe if the peer is there?

Or, better yet, am I missing some functionality in JXTA that will take 
care of this for me?

thanks much!
  -john.