Here I am going to describe how to receive glucose values and entered data from Juggluco running on one phone to Juggluco running on another phone, when both phones are only connected to the internet via a mobile data connection. If you want to connect two phones only over the home network, see: devices without NFC to connect via Bluetooth with the sensor.
In this description I use a Android device at home as a go between. You can also run Juggluco server on a computer.
The current setup is the following: Freestyle Libre Sensor->Realme phone<->Modem<->Tablet<->Modem<->Sony Phone
The most difficult part is forwarding an extern port from the modem to the device acting as intermediary (the tablet). This will be different on different modems. I will describe here how to do it on my own modem, so that you have an idea for what to look in the user manual of your modem.
First you have to "create" an application, which in reality is nothing more than giving a particular port a name. I call this application port8795 and use port 8795.
After this you have to assign this application to a local device. We use the device I have called M5. Somewhere else in the modem interface, you can find that this device has IP 192.168.1.69 and that is the home network IP of my tablet.
External netwerk connections to port 8795 of the modem are now forwarded to port 8795 on 192.168.1.69.
We have to find out what the external IP of the modem we have to connect to. You can find this in the modem interface or simple by visiting https://www.showmyip.com from a device on your home network.
I found that my external IP was 188.8.131.52.
On my tablet I now run Juggluco listening on port 8795, so that the smartphone can connect to it from the internet.
My Realme phone is connected to the sensor and should send data to my tablet. On this phone, I go to left middle menu->Mirror->"Add Connection", specify the external IP of my modem (184.108.40.206 ). Don't set Test IP. To differentiate the different connections, we give it the label "realme". The connection on the phones should be set "Active only". We set what should be send to the tablet (Amounts, Scans and Stream) and specify a password for example "PassRealme". Specifying "Scans" when using Libre3 is a little bit strange, but you should also set that when you send Stream. You can leave you Amounts or set only send Amounts if you want. Press Save.
On the tablet we should specify the other side of the connection. "Passive only" because the phones are not accessible from the internet. Don't set Test IP. Set "Test Label" with the same label as on the Realme phone. set "Receive from" and the same password as on the other side of the connection (for example "PassRealme"). Press Save.
Go back to the tablet to specify the other side of this connection: Unset "Test IP", set "Test Label" with the label we also set at the other side of the connection, "sony". Set "Passive only", set what to send: "Amounts", "Scans" and "Stream". Set the same password as at the other side of the connection and Save.
Sync on the Sony phone should start the reception of data from the tablet.