How does Windows know how to resolve mDNS queries?

Question

When you install Bonjour for Windows you can resolve any ".local" mDNS name from anywhere in the system.

For example, you can "ping some_computer.local" and mDNSResponder.exe (Bonjour/mDNS Daemon) will respond.

However, mDNS operates on port 5353 so how does Windows know how to resolve these DNS queries?

Is mDNSResponder.exe hooking into the Windows DNS Resolver somehow?

Answer 1

Bonjour for Windows allows any software using the standard name resolution APIs to resolve mDNS names; it does so by registering a DLL (mdnsnsp.dll) as a namespace provider using WSCInstallNameSpace.

The corresponding code is included in the mDNSResponder source (in particular, look at the mdnsNSP and NSPTool components).