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Read about the [[general concept of *inter-process communication* (IPC)|/ipc]].

On Mach, an IPC is done by invoking a [[port]].

The two fundamental operations, to *send* and *receive* [[message]]s, are used
to implement a [[RPC]] system.

[[Sequence_numbering]].

[The Unofficial GNU Mach IPC beginner's guide](http://www.nongnu.org/hurdextras/ipc_guide/ipc_guide.html)