I have a process (dbus-daemon) which has many open connection over UNIX sockets. One of these connections is fd #36:
=$ ps uw -p 23284
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
depesz 23284 0.0 0.0 24680 1772 ? Ss 15:25 0:00 /bin/dbus-daemon --fork --print-pid 5 --print-address 7 --session
=$ ls -l /proc/23284/fd/36
lrwx------ 1 depesz depesz 64 2011-03-28 15:32 /proc/23284/fd/36 -> socket:[1013410]
=$ netstat -nxp | grep 1013410
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
unix 3 [ ] STREAM CONNECTED 1013410 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
=$ netstat -nxp | grep dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1013953 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1013825 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1013726 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1013471 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1013410 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1012325 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1012302 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1012289 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1012151 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011957 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011937 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011900 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011775 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011771 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011769 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011766 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011663 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011635 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011627 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011540 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011480 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011349 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011312 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011284 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011250 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011231 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011155 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011061 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011049 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011035 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1011013 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1010961 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
unix 3 [ ] STREAM CONNECTED 1010945 23284/dbus-daemon @/tmp/dbus-3XDU4PYEzD
Based on number connections, I assume that dbus-daemon is actually server. Which is OK. But how can I find which process is connected to it – using the connection that is 36th file handle in dbus-launcher? Tried lsof and even greps on /proc/net/unix but I can't figure out a way to find the client process.
Best Answer
Quite recently I stumbled upon a similar problem. I was shocked to find out that there are cases when this might not be possible. I dug up a comment from the creator of lsof (Vic Abell) where he pointed out that this depends heavily on unix socket implementation. Sometimes so called "endpoint" information for socket is available and sometimes not. Unfortunatelly it is impossible in Linux as he points out.
If you look at /proc/net/unix you can see for yourself, that (at least on my system) he is absolutelly right. I'm still shocked, because I find such feature essential while tracking server problems.