Hi, I have a similar use case, but in my tests none of this is working properly. It seems every component that does some kind of data aggregation and/or delivery brings unforeseeable and unacceptable consequences. Modbus has massive memory leaks. The longer you run it the more memory it consumes. Latency and cpu usage for Modbus is also horrible. I have machines with a 3rd of the power and memory that are more stable and soooooo much faster. For example a Pokeys57e (a cheap little IO module) has an average latency of 1ms at almost 1000 queries per second. The RUTX12 has an average latency of 30ms at 5 queries a second. And if you query multiple registers latency can get up to almost 2000ms! Anything over 5 queries per seconds raises CPU usage to a point that you can hardly do anything else with it. To be fair, this is MCU vs CPU which is an unfair fight but those are still sad stats.
{ edit : memory usage rose to 33.7% by the time I was done writing this }
{ edit 2 : memory usage 41.7% three hours later. Total memory usage is already at 98% in under 24 hours uptime. you get the idea. This is unusable :-( }
Data to server blocks queries to the GPS module. As long as its running coordinates are not available to other applications. This is unacceptable because its a no brainer that so many applications shouldn't simultaiously be reading from the hardware directly. But one application could poll the hardware and share the data via unix socket. Then 50 apps could access the data at the same time without problems.
This is all on the RUTX12 so I'm not sure if the RUT955 runs better. But its a shame because these are not consumer toys. And "industrial" doesn't just mean temperature ranges but robust software as well. Also the fact that everything is based on openwrt, but they cut us out of the native package manager! This of course leaves gaping security holes and no way to patch them if they don't issue an official update and the user doesn't know how to use the command line.
This is also my first experience with Teltonika, I'm not impressed so far. It's the nature of the issues that concern me. And the fact that many of the issues are fixable, I've fixed many here unmentioned myself. Everything visible is extreeeemely beautiful and polished. Almost too polished in relation to the issues at hand. The RUTX12 is a new machine so I'm still kinda hoping for updates. I still have hope because it is a really great concept if it actually worked. That said, if you consider where Modbus is used it's never good to release a product to market if it's faulty. Even the most cheaply made china products don't fail on Modbus.
I would run a test with one before you invest in a fleet like I almost did.