I guess it not only depends upon the number of clients but rather upon the amount of data, the frequency with which they arrive and the processing involved on them. If all your clients are just bombarding data onto the server at high speed then maybe you should use a thread for the processing so that you dont loose the packets that arrive while the processing is being done. But again, it also depends upon the criticality of the packets - UDP is fundamentally for unreliable communication. You can ofcourse build your own app protocol to enforce reliability, but if the packets are not so critical and you can live happily even if you loose a few, then you can just do without the thread. Also, keep in mind that there would be a number on maximum number of threads that a process can spawn, which could be different for different systems. In such a case you should also have a strategy to deal with incoming requests when you have already spawned that number of threads.

Hope that gives some ideas..

Animesh.