On 27/12/2020 12:42, Chris Green wrote:
> 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!

Why? a smart phone sim is a charge per gigabyte, They are always on for
data!

>
>      So, is there software for Linux (and thus for the Pi) which will
>      handle incoming calls to allow ssh login?
>
Just use an IP capable dongle forget about 'incoming calls' and ssh
riught in. Biggest problem will be on what IP address you appear,

>      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?
>
3G/4G is not 'dial up!

> Any/all ideas would be very welcome.
>

Look I think you have got the wrong end of the stick about how mobile IP
works...where is this pi going to be? Do you have a fixed IP address on
your ISP interface?

Its almost impossible to set up a mobile connection to receive
unsolicited  IP. The mobile provider will absolutely do massive NAT. So
you need the Pi to be always online and connected to something that you
can contact, and the figure out a way to hijack the link. Just running
keepalive packets wont break the bank.

sshing in wont be trivial but without knowing what you want to do with
the pi its hard to say whether you need to,. For example just polling a
webserver the pi could detect a request for data and uplaod it to the
webserver where you could download it., Even to the point of downloading
a command line off the server executing it on the pi and sending stdout
back to the server...


> 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.
>
>
Start with the assumption that you cant open a connection to a mobile
equpped pi, but 'always on' FROM the pi  wont be costly.

--
How fortunate for governments that the people they administer don't think.

Adolf Hitler

--- SoupGate-Win32 v1.05