The Natural Philosopher  wrote:
> 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 does just trying to connect *to* the device which has the data sim
dongle wake up the connection?  It means one needs a dynamic DNS
service but that's not a big problem.


> >
> >      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,
>
Yes, as I said it needs a dynamic DNS service but that's all.

> >      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?
>
I probably have got it all wrong!  The Pi is actually a Beaglebone
Black but that's irrelevant.

All I want to do is be able to use ssh to connect *to* the BBB from
home computers which have an internet connection.  The BBB doesn't
have WiFi available.


> 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.
>
Currently it uses (rather flaky) marina WiFi and sets up ssh reverse
tunnels by connecting to an intermediate system so that I can then
connect *to* it via the intermediate system.

I am looking for something more reliable.

> 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.
>
So, if one has 'always on' FROM the pi does that then just require
some sort of dynamic dns service to be able to ssh *to* it?

--
Chris Green
·

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