The QNX Kernel supports three kind of interprocess communication: messages, proxies, and signals.
Messages are the fundamental form of IPC in QNX. They provide synchronous communication between cooperating processes where the process sending the message requires proof of receipt and potentially a reply to the message.
Proxies are special form of message. They are especially suited for event notification where the sending process does not need to interact with the recipient.
Signals are traditional form of IPC. They are used to support asynchronous interprocess communication.