Google Notice on Service Discontinuation
Google Notice on Service Discontinuation

A few months ago, I got a notice stating Google Hangouts would stop handling SMS/Voice. In 2012 I transfered my primary phone number to Google Voice before leaving the country, so I could still send texts and keep my American number. At the time, it cost $20 to transfer a number to Google Voice. Eventually Voice was deprecated and Google moved their customers’ phone numbers into Hangouts. Now they’re moving everything back to Voice apparently, in their never ending confusingly labeled and hopelessly broken suite of communication tools. Rather than wait for Google to finally put their telephony products out of their misery1, I decided to port the two phone numbers I had on Google over to another service. After some experimenting and trials with various providers, I decided to go with which allows for both Session Initiation Protocol (SIP) for voice calls and XMPP for texts/MMS.

Twilio Sucks

At first, I was looking at moving all my phone numbers to services on Twilio. I found a blog posts for setting up SIP, however the instructions were complex and quite old2. I was able to get basic voice/SIP working, but not reliably. Twilio also enforces 2-factor authentication after initial account setup, but only allows for SMS 2FA. Since I intended to port my phone into Twilio, I would have rather used another form of 2FA such as an OTP Secret. Twilio may support other 2FA, but I couldn’t get past the login screen without giving them a phone number.

Twilio seems insanely complex for those without a strong background in telecommunications software development. I also realized I would need to do a considerable amount of coding and testing if I wanted to get SMS/MMS messages working with my existing matrix server. Finally, Twilio broke their contract with Parler, showing that they were complicit in the new dangerous era of corporate censorship. I realized they are not a company I would want to purchase services from, and decided to look at other options. is a service that has more batteries included. It provides a gateway to connect phone numbers to SIP for voice and XMPP for texts and media. I like this model as it lets me bring my own self-hosted XMPP server and SIP software or hardware devices. I started by using a number provider by and testing it against my own XMPP server. Once I was satisfied that text, media and voice worked as expected, I ported both of my phone numbers from Google Voice.

My Google Voice Billing History
My Google Voice Billing History charges $34.99 (USD) per year for their services. Google charged me $3 per Google voice number in order to unlock and port them. The porting process is fairly straight forward.

Google Voice Number Porting Screen
Google Voice Number Porting Screen
Google Voice Warning for Unlocking a Phone Number to be Ported
Google Voice Warning for Unlocking a Phone Number to be Ported
Purchase Confirmation for Google Voice Number Unlock
Purchase Confirmation for Google Voice Number Unlock


Most stock Android phone dialer applications support VoIP phone numbers via SIP. On my Sony Phone, these options can be found under Settings > Calls > Calling Accounts. Here I can add SIP accounts, and setup my device to ask which phone number I want to use for each call. The UI also indicates if the SIP connection is working correctly to receive calls. In the following screen shots, you can see how one of my SIP accounts is setup correctly and one indicates it cannot authenticate (in this case, due to using the wrong password).

SIP Setup on my Android Phone
SIP Setup on my Android Phone

SIP is a standard found in many software telephony services and hardware devices. I can setup the same SIP accounts in Linphone, an open source VoIP software option. When a phone call is made to one of my registered numbers, it will ring both my Android phone setup with SIP and my software Linphone. The first device I answer with will be used for the voice session. The only tricky part of using Linphone with are the account settings. Through some trial and error, I discovered that the SIP address should be set to (replacing the 555 with your actual phone number) and the SIP Server address should be <;transport=udp>.

Update: After you specify the SIP address and server address, you will be prompted for credentials where you should put in your username and password. For, the username typically has the format (userid)~40(xmpp server host). reached out to me to say having multiple SIP clients connected and listening for calls isn't officially supported, and is not guaranteed to always work. They also support voice via XMPP as well, if you don't want to use a separate SIP client.(Updated: 2021.06.01)
Linphone SIP Account Setup
Linphone SIP Account Setup

There are many hardware devices that support multiple SIP accounts as well. Sometimes these can be found on eBay from businesses who are getting rid of old hardware, allowing you to setup a physical VoIP phone in addition to software phones and mobile devices.

Sync Contacts from CardDav to XMPP

Several years ago I stopped using Google Calendar and Contacts. I migrated to Radicale, an open source CardDav/CalDav server that I host myself. This puts me in full control of my contacts and schedule without relying on services from Google, Apple or others. On my Android device, I disable Google syncing and instead, I use DAVx5 to synchronize calendars and contacts to Radicale. This works fine for linking contacts to incoming or outgoing SIP calls, but for SMS, I need to sync my CardDav contacts with my XMPP roster. That way I can see all my contacts using the open source XMPP client Conversations on my phone.

There is a vCard specification for XMPP, but I’m using an XMPP to SMS gateway from All SMS messages would go through the special gateway transport Rather than modify my existing contacts to add an XMPP field, I wrote a python script to sync my contacts to my XMPP roster, adding in the correct gateway. It’s configured with some very simply YAML:

  username: yourusername
  password: S0m3pa33w0rD
  password: Sup3rS3c4e7Pa33w0rDee
  number_type: cell
  number_prefix: "+1"

It’s easily runnable via Docker using environment variables:

docker run --rm -it \
    -e CARDDAV_URL= \
    -e CARDDAV_USERNAME=djsumdog \
    -e CARDDAV_PASSWORD=s0mepa33w0rd \
    -e \
    -e XMPP_PASSWORD=p1rates \
    -e SYNC_NUMBER_TYPE=cell \
    -e SYNC_NUMBER_PREFIX=+1 battlepenguin/dav-xmpp-sync --verbose --dry-run sync

The docker image can also use a configuration file mounted from a volume:

docker run --rm -it -v $PWD/config.yaml:/app/config.yaml battlepenguin/dav-xmpp-sync --verbose --dry-run sync

It can also be run directly by checking out the source from git:

git clone
cd dav-xmpp-sync
pip3 install --user -r requirements.txt
python3 --dry-run --config config.yaml sync

Running the script directly will give colored output.

Thoughts about

There are some things to keep in mind about

  • Service is still in beta
  • You cannot set your own SIP password. They are three words long and auto-generated.
  • Most of’s backends are open source services if I ever want to attempt to host telephony myself.
  • only allows for 120 minutes for SIP calls per month.
  • Unlimited incoming SMS/MMS
  • Service intends to be in beta until at least the summer of 2021
  • Customer support is over XMPP Chat and, so far, has been very good
  • Phone numbers can take up to a week to port

Closing Thoughts

Google Hangouts/Voice was the last major service which kept me logged into Google. After testing out and porting my numbers to, I logged out of my Google account and deleted all my Google and YouTube cookies on my web browser. I hope continues to grow into a viable service. Considering how confusing Google’s messaging services are, how they’ve destroyed e-mail reliability, and how they tend to kill off most of their products1, I feel pretty good about moving one more thing away from their ecosystem.

  1. Killed By Google. Retrieved 25 May 2021.  2

  2. Register a SIP Phone Directly to Twilio and Make and Receive Calls. Klein. Twilio Blog. 28 Feb 2019.