If the up.time Linux Agent is managed by xinetd (default option), it is possible to limit access to the Agent with xinetd's "only_from" parameter. Setting only_from parameter to the up.time Monitoring Station hostname or IP address will restrict any other system from issuing requests to the up.time Agent.
To implement, update the /etc/xinetd.d/uptimeagent configuration file and add the following line at the end.
only_from = uptime_ms
If using an IP address, the only_from line is similar:
only_from = 10.1.1.1
With the /etc/xinetd.d/uptimeagent configuration file updated, restart the xinetd service to read in the change.
/etc/init.d/xinetd restart
Now, only the up.time Monitoring Station system can access the up.time Agent.