Not Giving Up On iThreads

Elizabeth, et al.:

Some designs seem to beg for threading solutions.  I have rearranged my
project in a way that hopefully accommodates the use of ithreads.  I'm
hoping to get some feedback here.

Many thanks to Jay Flowers who posted a model for a TCP Login Server in
this forum which I have customized and implemented successfully.

The current challenge is to create a UDP message server the purpose of
which is to listen for client requests and respond with client-specific
messages (the messages are stored in a hash).

Each UDP socket can support 20 clients before it is overloaded. 
Therefore, I need to spawn a new socket for every 21st client.  Each
socket stays open until there are no more clients assigned to the
socket.

Questions:

1) Can threads be used effectively for this design?
2) Can a hash be shared amongst the threads for the message lookup?
3) Is it safe to leave threads open for extended periods of time?
4) Is there a way to pass data from the thread back to the "parent"
without closing the thread?

Thank you very much for sharing your ideas with me.

Steve