'''PRUDP''' is a third-party network protocol used for network communications by some Nintendo software on the 3DS. It presumably stands for "pretty reliable UDP" or "partially reliable UDP" or some such, and essentially implements TCP-like reliability via sequence numbers and acknowledgement within UDP. Optionally it also adds security (prudps). This is probably used for online comms in most(?) 3DS games.
At least two different versions of PRUDP seem to be used by Nintendo software: an older version used in the [[Friend Services|Friend services]] and a newer one used in Pokémon X/Y.