Only the PMU Connection Tester on the second machine should be fine.
If you are using a Windows machine, you will need to open the "Windows Firewall" settings that can be found in the control panel.
Once you have opened the firewall settings from the control panel, the simplest thing to do is to click on the link called "Allow an app or feature through the firewall", click on "Change Settings", then click on "Allow another app...".
From here you would browse the openPDC executable, typically "C:\Program Files\openPDC\openPDC.exe" and click "Add".
Once added the openPDC will appear in the list of firewall exceptions as "openPDC Iaon Host", make sure you click at least "Domain" and "Private" options for access to the service and "Public" if you wanted to hit the service from the Internet.
Doing this should allow all openPDC services to be accessed from remote computers.