You want only particular remote hosts to access a TCP service via inetd.
Use tcpd, specifying rules in /etc/hosts.allow and/or /etc/hosts.deny. Here's an example of wrapping the Telnet daemon, in.telnetd, to permit connections only from IP address 192.168.1.100 or the
example.com domain. Add to /etc/hosts.allow:
in.telnetd : 192.168.1.100 in.telnetd : *.example.com in.telnetd : ALL : DENY
Then modify the appropriate configuration files to substitute tcpd for your service, and restart inetd.
The control files /etc/hosts.allow and /etc/hosts.deny define rules by which remote hosts may access local TCP services. The access control daemon tcpd processes the rules and determines whether or not to launch a given service.
First set up your access control rules in /etc/hosts.allow and/or /etc/hosts.deny. Then modify /etc/inetd.conf to invoke the service through tcpd:
Old /etc/inetd.conf: telnet stream tcp nowait root /usr/sbin/in.telnetd in.telnetd New /etc/inetd.conf: telnet stream tcp nowait root/usr/sbin/tcpd /usr/sbin/in.telnetd
Finally restart inetd so your changes take effect. [Recipe 3.4]
hosts.allow(5), tcpd(8), inetd.conf(5).