For a UDP socket, sendto() will attempt to bind an ephemeral port. For a Unix domain socket of datagram type, since there is no port concept, only a path address, does sendto() try to come up with a random path(which needs to be backed by a real file in the fs), or a random abstract path(such as '@blah'), and then binds to it?
I am asking because on my machine I see these datagram Unix socket pairs in 'ESTAB' state, and I wonder how are these endpoints identified if the address here is '*', which I guess is a NULL string?
# ss -xp | grep dev-log
u_dgr ESTAB 0 0 /run/systemd/journal/dev-log 15236 * 0 users:(("systemd-journal",pid=254,fd=3),("systemd",pid=1,fd=36))
# ss -xp | grep 15236
u_dgr ESTAB 0 0 /run/systemd/journal/dev-log 15236 * 0 users:(("systemd-journal",pid=254,fd=3),("systemd",pid=1,fd=36))
u_dgr ESTAB 0 0 * 19250 * 15236 users:(("dbus-daemon",pid=369,fd=14))
u_dgr ESTAB 0 0 * 21686 * 15236 users:(("dbus-daemon",pid=701,fd=10))
A related question is, what are those numbers in place of port numbers mean, in unix domain socket world?