I have a tangentially related problem I have been battling with that you may be able to help me with. I'm moving overseas (Australia to Denmark) and would like to keep my current mobile phone number working for calls and SMS , but use it from afar. I would be able to leave a raspberry pi at a friend's house. Can you use this setup without a SIP provider? Would you need to buy a modem for the raspberry pi?what would you do?

I've never done it, but look into chan_mobile and a bluetooth dongle to connect a mobile (with your SIM) to asterisk running on a Pi at your friend's place.

I would just port my number to twilio and use/write a really basic twilio mobile app. It's a bit risky to rely on a slightly cobbled hardware/software setup that is sitting across the world with no physical access.

Note that one problem with voip providers is the numbers/lines often won't be recognized as valid by snake oil 2FA and the like. So porting to a voip provider only works if your goal is receiving SMS/calls from actual humans or just parking the number for later. But if you're doing it to avoid having to change your number for every service that has an SMS nagwall, it likely won't work.

You can get a modem that will do SMS (eg a Sierra Wireless card), but I don't know if/how they do voice.

Also, I'd shy away from the RPi based on the unreliability of SD cards. It would/will be pretty annoying for your host to go down and you have to travel back to fix it. I suppose if your friend is halfway handy you could keep an imagine of the machine as installed, and if the root filesytem goes wonky, have your friend pull the card and reimage it.

I've been using a voip number for all my sms 2fa needs for the last 5 years while living abroad. I have a dozen banks and other financial institutions plus the irs happily accepting it. Some companies, like openai, wont accept it, for those I just buy single use SMS numbers.

I've had problems with a bunch of places, so it's at least YMMV then. And I'd be wary of transferring an existing number in (as opposed to getting a new voip number and then setting it up).

I'm sure specific services are hit or miss - there really shouldn't be a problem sending SMS to whatever number a user enters, but paternalistic snake oil salesmen gonna be paternalistic.

I've had the least difficulty with Google Voice (I believe it's impossible to tell "Google Voice" usage from bona fide Fi usage where it's really the users' only phone number). Voip.ms has worked very little for me, to the point of that I don't even try it. Heck I even used a voip.ms number for some online classifieds, and another person using Comcast/Xfinity mobile couldn't text me. I'm not saying this as a slight against Voip.ms itself, from what I've gathered most voip providers will be treated similarly.

One of these days when I get around to it I plan on setting up a wireless modem on a $3/mo paygo plan for my SMS nag needs. With a script that automatically brings the number as close to my paste buffer as possible.

What single use SMS service do you use? I haven't really investigated those.

> I believe it's impossible to tell "Google Voice" usage from bona fide Fi usage where it's really the users' only phone number

These are definitely distinguishable, and some auth service treat them differently. Google Voice numbers come from a different carrier (the one named Bandwidth) than most Fi numbers.

Some services can definitely detect Google Voice. Chase bank won’t send SMS to voice.

I have a Chase account, they send 2fa texts to my voip number ok, but it's not Google Voice, it's another service.

"One of these days when I get around to it I plan on setting up a wireless modem on a $3/mo paygo plan for my SMS nag needs. With a script that automatically brings the number as close to my paste buffer as possible."

This is called a "2FA Mule":

https://kozubik.com/items/2famule/

"A 2FA Mule is a mobile phone configured to forward SMS 2FA codes via email."

I use something similar. A dedicated app makes a POST request to my Google Apps Script as soon as any sms arrives at my second phone. That script sends it in a Telegram Bot Chat to all of my devices.

I use a RedPocket (GSMA Flavor) $60/year for my resume and 2FA number as an eSIM.

I turn it on when needed, which is almost never. When not job searching, the voicemail plays the classic "this line has been disconnected" tones and message on repeat for two minutes. WiFi calling means I can use it anywhere I have WiFi.

I get incredibly few spam calls using this strategy.

There are two different reasons companies ask for your phone number, and it's worth distinguishing between them:

The first is for sending a verification code during signup to prevent spammy/abusive signups. In my experience, this is the least likely to work with VoIP numbers because companies often intentionally block VoIP numbers.

The second is for sending 2FA codes during login. My experience with this has been much better. AFAICT, companies do not intentionally block VoIP numbers for this use case. When SMS does fail, there is almost always an option to send the code by voice call, and this is always 100% reliable.

I also have some experience with using a modem with a SIM card to receive SMS. I've used two different models of modem (not Sierra Wireless) and both have been very flaky, often locking up and requiring a power cycle, or having hours-long delays when receiving SMS. I would not call this approach a panacea.

Unfortunately, Twilio is no longer a viable option for sending SMS for personal use. If you want to send SMS you have to register a "campaign" and jump through a bunch of hoops that assume you're a company sending a large volume of application-generated messages (e.g. you must disclose samples of the types of messages you intend to send, and get explicit opt-in from recipients). Up until now, I've managed to avoid registering a campaign by instead paying a slightly higher per-message cost, but this is being phased on on July 5. I've been trying out https://jmp.chat (their founder is commenting elsewhere in this thread) and will likely port my number to them.

Hmmm ... I think the July 5 deadline is specifically for UK recipients ?

Regardless, your overall impression is correct: Twilio is no longer a hacker/hobbyist/enthusiast option as you cannot (by the letter of the law, at least) send SMS without registering your business entity:

https://twitter.com/rsyncnet/status/1593384850073214976?lang...

This is very troublesome to me because I have built my own personal telco out of twilio functions and twiml bins, etc., and am heavily reliant on all manner of SMS workflows.

As of this writing (2023-05-27) everything - even SMS delivery to T-Mobile numbers - continues to "just work" but it sounds like I will just wake up one morning to have it all broken ...

The deadline is for US recipients:

> • Effective July 5, 2023, all 10DLC phone numbers used to send SMS and MMS messages to U.S. phone numbers must be fully registered to an approved campaign under your brand. Messages sent using unregistered phone numbers will be subject to a gradual increase of message blocking by Twilio, beginning on July 5, 2023, ultimately leading to a full block of all unregistered U.S.-bound messages sent after August 31, 2023.

Source: https://support.twilio.com/hc/en-us/articles/1260800720410-W...

I have setup a PRI to SIP channel before using elastix (now discontinued and bought by 3CX I think).

This needs investigation, but - Over the top of my head, I think you could probably have some kind of a 4G/5G modem hooked on to an SBC (Pi, APU, etc.) and then forwarded to your SIP line which you can pick over IP (Internet), this should work.

One of the child comments mentioned DID (Direct Inward Dialling). I am no expert, but if your Australian provider supports something similar, you will get the number (friend) who is dialling in, instead of your own Australian number dialling in to your receiver phone. This is useful for caller ID, otherwise it's just like a forwarded call.

Hope this helps.

This is pretty much exactly the problem that we originally created https://jmp.chat to solve, no sip or complex setup needed these days for that use case.

I heard about you ages ago and wanted to use your service ever since. The only problem I don't need it for anything. But I'm glad you you are still there.

I use Callcentric for this. Ported a land line over years ago. It now has SMS which I can do using the Callcentric app. And it forwards voicemails to me with email. Otherwise I don’t use that line for actual calls anymore.

I've been working with bespoke VOIP/asterisk systems for a decade, I have one bit of advice to add - consider toll fraud. Especially for a system accessible from the internet. If an attacker can figure out how to make calls through your PBX, they can rack up tens of thousands of dollars in tolls over the course of a night.

Most of the integrated FOSS solutions come with fail2ban already configured, it is essential. If you want more peace of mind, a prepaid trunk helps. That means you charge up your sip trunk account, and if someone drains it, it just stops working instead of continuing to drain your bank account.

You can also limit international calling on your trunks, which effectively nullifies the financial drain of this kind of attack (though it's still obviously bad if an attacker can access your system in any way)

It's surprising that you could configure everything without hardware/software compatability issues.

Well I basically used a a Linux distribution made precisely for this: it was called "RasPBX" back then, IIRC. The hardware was simple: a Pi 1, an external HDD hooked through USB to the Pi and Cisco VoIP phones. That Linux distro already took care of picking software components/versions all working fine together and it was tailor made for the Pi. It was pretty plug and play from what I remember.

I'm a software dev, not a sysadmin, but I can find my way around configure Linux machines.

I don't remember it as being particularly complicated. What I do remember for sure though is that once it worked, it worked flawlessly for years.

I believe they're still related but the guys at Nerd Vittles [0] are still doing a PBX in a Box style deployment. Looks like it's called Incredible PBX [1] now. But the last time I ran it it took a lot of considerations around running SIP securely and brought a few of the pieces together. Probably worth a look if you're interested in self-hosting at home or for SMB.

[0] https://nerdvittles.com/ [1] https://wiki.incrediblepbx.com/

Nerd Vittles is alive and well. And Incredible PBX now offers dozens of free, turnkey platforms. Have a look at wiki.incrediblepbx.com for suggestions.