we have a 2008 R2 server with Realport, a portserver TS 16 with modems RTC.
A soft calls a lot of weather sensors.
When this soft do several calls simultaneously on several ports/modems, it often fails.
When the same soft do the same calls with few seconds between them, the result is better.
I’ve never heard of this behavior before. These products are designed for simultaneous serial port connections/activity.
Have you contacted your software company? Sounds like the software may be getting confused when dealing with multiple connections.
You can test simultaneous connections quite easily using a terminal emulator, such as, PuTTY and establishing multiple PuTTY connections to multiple serial ports.