The Postfix master daemon opens three sockets per master.cf entry:
the service endpoint (the first field in master.cf), plus one
socketpair. This single socketpair is used to receive updates from
all the child processes that implement the corresponding master.cf
service.
The current stock master.cf file has 24 entries. One is a TCP service
and the remainder are UNIX-domain sockets. That corresponds with
one TCP socket and 71 UNIX-domain sockets.
With older master.cf files, two of those UNIX-domain services used
to be FIFO services, That corresponds with one TCP socket, 69
UNIX-domain sockets, and two FIFOs.
Based on your count of 65 sockets, I suppose that your master.cf
file has 22 entries (one TCP service and 21 UNIX-domain services).
System library routines may open other sockets or files, for example,
to talk to nsswitch.conf services. The Postfix master daemon has no
control over those sockets or files.
Wietse
