Help with small network / remote data access technologies

Hi,

I have a small network of 8 mobile 'nodes' ? Each node is a self contained system with 6-10 computers, 2 WAN sources, and a router. WAN is through SAT coms or Cellular modem.

On each 'node' there is a server at 192.168.1.100. This server provides data that I need at the central location. I need to be able to query the server and automatically populate a database.

I have been using TeamViewer and RealVNC to access these nodes, but I need something different. I need to be able to make a connection with one node, collect data, close connection, move to the next 'node'.

I have not been able to get Windows VPN server to work, not even on my local network. I have had varying levels of success with BitVise and SoftEther, but never able to work over the internet, and I don't know if that software is even quite what I want.

I tried setting up NeoRouter, however the required port is blocked ? This is over a cellular connection. Oh, and I set up DuckDNS and that seems to work, but I think my ISP might be blocking and I'm out of luck there.

I need something that works like TeamViewer, in the way it connects. Or I need to do what TeamViewer is doing in order to make the other software work.

ISP is ATT.

Thanks for any ideas !