ALPC & local RPC
Fast local message passing used under the hood by several Windows components on the same machine.
What you should already know
This topic is marked expert. Skim these first if any of them feel unfamiliar.
Official Microsoft docs
Closest official references related to this topic on Microsoft Learn.
Why it matters
This is the low-latency path behind many same-machine component interactions, especially when Windows services and system processes need structured communication.
Mental model
ALPC is the transport-level message fabric; supported frameworks such as local RPC use it instead of asking applications to speak native ALPC directly.
How it works
- 1Clients and servers communicate through local ports rather than through network transports.
- 2Messages are exchanged asynchronously and can carry structured payloads and handles.
- 3Most application code uses higher-level frameworks such as RPC over ncalrpc rather than native ALPC APIs.
Key terms
- ALPC
- Advanced Local Procedure Call, the asynchronous local message mechanism used by Windows.
- ncalrpc
- The RPC protocol sequence for efficient same-machine RPC.
Talking to a local security component
A process may invoke a supported local RPC interface that internally rides on ALPC rather than opening raw sockets or files.
Common misconception
ALPC is not the recommended app-level API. It is better seen as plumbing that supported frameworks build on top of.
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