Here's some sample content of /usr/local/etc/rsyncd.conf to serve 
files from a particular directory to certain addresses:


# global settings here
uid = nobody
gid = nobody
use chroot = no
max connections = 5
syslog facility = local5 
log file = /var/log/rsyncd.log
pid file = /var/run/rsyncd.pid
read only = yes
list = no

# define a specific module
[rbl]
        path = /some/path/here
        comment = RBL zone files
        read only = yes
        list = yes
        uid = nobody
        gid = nobody
        ignore nonreadable = yes
        hosts allow = 1.2.3.4 10.20.30.40


Where you need to fill in the appropriate path to the files,
IP addresses to allow, adjust the logfile and pid paths 
appropriately, etc.

For more information, please see: man rsyncd.conf