"Chris Green"  wrote in message
news:83cmbh-3vl4.ln1@esprimo.zbmc.eu...
> Are there any simple 3G/4G add-ons for a Pi that will allow it to
> power up into a mode where it has the ability to be connected to via
> the mobile data connection?
>
> I want a system that I can connect to from my home desktop/laptop on
> demand.
>
> Sort of 'thinking out loud' about this:-
>
>    I suppose a USB 3G/4G dongle could provide the hardware required
>    to make a mobile connection to the PI, recommendations?
>
>    It has to 'connect on demand' dialling *to* the Pi, it can't keep
>    the line open all the time, very expensive!
>
>    So, is there software for Linux (and thus for the Pi) which will
>    handle incoming calls to allow ssh login?
>
>    How does one manage the other end?  Is there Linux desktop
>    software to allow one to dial up a remote system and then squirt
>    ssh down the connection?
>
> Any/all ideas would be very welcome.
>
> I'm happy with fairly low-level stuff, I am a retired software
> engineer, grew up with Unix (solaris) command line and I'm also quite
> into home-build electronics projects.

As I understand it, data connections (as opposed to voice connections) are
permanently on and don't accrue connection charges. You get a standard
amount of data per month that can be transferred over the connection, which
varies according to the tariff.

So you need a USB mobile data device and a SIM with a suitable data tariff.
Then you need a means of connecting to the Pi, in the same way that you
would if it was connected by Ethernet/wifi to your home network. VNC Server
on the Pi and VNC Client on the computers that will connect to the Pi will
give you a remote desktop. There maybe ways of doing it with PuTTY or other
ssh terminal apps, though I'm not sure how those handle you being connected
by a public WAN rather than LAN: I've only used Juice SSH on my mobile phone
for connecting to my Pi over my private LAN.

Since you will be running the Pi headless, one little hint (in case you
haven't discovered this already) with the Pi 4: you need to tell the Pi to
boot even if it can't find a monitor connected by HDMI and to set the video
mode which would normally be negotiated between Pi and monitor at boot time.

modify /boot/config.txt:

     hdmi_force_hotplug=1 # allow Pi to boot with no monitor connected
     hdmi_group=2
     hdmi_mode=82  # force 1920x1080x60 even though monitor can’t be
auto-detected

--- SoupGate-Win32 v1.05