Rsyncd: unable to bind any inbound sockets on port 873 I'm running OS X El Capitan.

I want to run rsync in daemon mode but I'm unable to do it. Here is the error from /var/log/system./log:

rsyncd[1329]: unable to bind any inbound sockets on port 873
rsyncd[1329]: rsync error: error in socket IO (code 10) at /BuildRoot/Library/Caches/com.apple.xbs/Sources/rsync/rsync-47/rsync/socket.c(477) [receiver=2.6.9]


Any advice?
You'd see that error if you don't have privileges or a process is already bound to port 873.
Anyway I just wrote a small 'one button' GUI app which starts the rsync daemon for you:
http://bonhardcomputing.com/rsync-server/
It also has the most modern version of rsync built into it...