Is there a log or config file you could post? If the client is like nrpe then maybe you need to specify the address to listen on. On NRPE if it’s not specified correctly then the service looks like it’s running but can’t bind to the port.
I don’t know of a guild for hpux. However the -n option for the client and the server should disable NRPE. You will need to change the start up script to us -n. I wouldn’t do this across the internet though.