What is rapportd and why does it want incoming network connections?
EDIT: It looks like the man page has been updated and now reads:
Daemon that enables Phone Call Handoff and other communication features between Apple devices.

I just had the same experience. The man page states that it is a:
Daemon providing support for the Rapport connectivity framework.
Checking the code signature with codesign -dv --verbose=4 /usr/libexec/rapportd shows it is signed by Apple and in a SIP-protected location (unless you turned off SIP), this appears to be legitimate Apple software. The man page implies it's related to communication, though I've yet to find any real documentation on it.
(Thanks to John Keates for the code-signature tip.)