Raspberry as dialin-server

Question

Want use raspberry in a place where isn't any WiFi, but got GSM coverage.

Need connect to the device - e.g. looking for a sort of GSM modem solution what will works as classic old-style modem-based inbound connections, e.g.

• in my PC i will use GSM modem to call
• and the raspberry will listen for the ring and starts "ppp" or "slip".

So, the question is

• it is possible?
• what type of HW i should to use - e.g. exists some GSM modem what allows inbound conncetions?
• the SW solution is probably something like here:
  • https://www.howtoforge.com/linux_dialin_server or
  • http://tldp.org/HOWTO/Modem-HOWTO-12.html

In short: how to connect to the raspberry where isn't any Internet? (some good guide with some exact solutions would be the best :)

Answer 1

Not all modems can be used for dial in. Almost all landline modems will work fine for dial in, but with GSM modems you need to verify that it will work. The fast easy way to check is to verify that it will sind RING messages and supports the ATA. If the modem meets those requirements it will work (with suitable adaptors). Install mgetty and read its documentation for software details. If the modem does not support those features there is still a slim chance it will work, but it will be much harder to setup. The modem bobstro linked to may work, but it is designed for other use cases (it is designed for continuous internet connection) and probably will not work with mgetty. Unfortunately you will probably need to talk to a salesman to find the right modem for your use case. If this is noncommercial you may also want to look at HAM based radio modems.

P.S. use ppp not slip. slip is better than nothing, but ppp is much easier to use.

Answer 2

Since Raspbian is based on Debian, if you buy a USB 56k modem and connect it to the Pi, you would probably be able to make the Pi listen for calls. I'm not sure how to do this exactly though, but it might help if you search Google for "Setup Debian as dialup server". It's most likely possible.

Answer 3

You can buy GSM modems but the modem itself is expensive, and you're going to need some sort of data plan for it. You can get models that connect via USB, or Ethernet.