So a couple of things on this.
The 3 devices which are operating as desired are 100% within the university's network. The server which is running OpenPDC is also within this network, and has been set to half duplex since installation. Or rather the port it is on is set to half and the server is on Auto negotiate.
2 of the 3 devices which are not functioning are technically part of the university network...but the setup is slightly different than the 3 functioning devices. These 2 devices are located on satellite campuses, which have network IPs leased within the main network, however for their traffic to come back to the main campus they must go over the open internet. Therefor I personally consider them to be external devices.
Further support of those two devices being "external" is the following. The final non-functioning device is 100% external to the university's network (installed at a third party location with an entirely different network.) This final device exhibits exactly the same behavior as the two previously discussed.
My opinion is that a firewall (or perhaps some other in-line security device) is causing this issue based on the following summarized reasons:
- I have 3 identical PMUs working properly with my server on the university's main network (i.e. the duplex setting of the server is not having an impact there.)
- The 2 devices which are on my university's network (kind of) were working properly in my lab for 2+ weeks, and only began not working when moved to the new location.
- These 2 devices act exactly the same as the final non-functioning device, which is 100% external.
I really just want to do as much investigation as I can from the application side of things (OpenPDC). It seems as though you have the same view point as I do, that the duplex setting is incredibly unlikely (but not impossible) to impact my setup?