Qnet is QNX Neutrino's transparent networking protocol.
It's described in the Using Qnet for Transparent Distributed Processing chapter in this guide, and in the Native Networking (Qnet) chapter of the System Architecture guide.
Qnet displays other QNX Neutrino machines on the network in the filesystem and lets you treat remote systems as extensions of the local machine. It does no authentication beyond getting a user ID from the incoming connection, so be careful when running it on a machine that's accessible to public networks.
Security policy offers some control over what processes on one node can do to another. When you are securing a node in a Qnet network, choose a policy that prohibits all Qnet access so that the secured node can use Qnet to communicate with other nodes and other nodes cannot connect to the secured one. Limit processes that can be connected to, over Qnet, to ones that are considered low risk.
To make Qnet more secure, you can use the maproot and mapany options, which map incoming connections (root or anyone, respectively) to a specific user ID. For more information, see lsm-qnet.so in the Utilities Reference.