Anyone has any experience with using 3G / 4G routers with SIM slot and setting up port forwarding on them so they can access Open Sprinkler from the internet?
A router model I am considering is TP-Link TL-MR6400 300Mbs 3G/4G LTE SIM slot
Does not work on most European mobile providers as you are behind their NAT and they don’t allow incoming connection requests to ips behind their SIM divice. An easy workaround is to install a raspberry pi and use VNC or Teamviewer to access that client and from their jump onto your opensprinkler. I use this as there is no other way that is straight forward to achieve this.
You could alternatively install a VPN server (your NAS or raspi at home could do that job) in a location that allows incoming connections. Then you have your remote location connect to that VPN server and through advanced routing you could make the remote client’s network accesible from you home network to which in turn you can connect remotely via VPN from anywhere.
I’m successfully using a mofinetwork.com router with a t-mobile data plan. The router is rather pricey, but I needed something more robust than a consumer grade hotspot for use in a very hot garage. To get around the NAT issue, I utilize mofinetwork’s option to provide a static IP through their cloud servers for an additional monthly fee. This allows me to access the OpenSprinkler directly through the internet. No special routing was needed other than a port forward in the router. The router looks to be capable of running other VPN clients which may provide a static IP as well, but I haven’t explored that option.