A Python implementation of converting a Twilio bridged call to a conference call
When using Twilio, a bridged call occurs when an incoming call leg (also known as the parent call) gets instructions (via TwiML) to <Dial> a <Number>, <Client> or <Sip> leg. This then creates the outgoing call leg (also known as the child call). In order to convert this bridged call to a conference call (to for example use attended/blind transfer or agent coaching), it is necessary to first update the child call with new TwiML instructions to <Dial> a <Conference>. This will then cause the parent call to get new TwiML instructions from it's action URL (if it exists). If the action URL returns TwiML to <Dial> the same conference, both parties will be able to continue talking.
python3 -m venv venvsource venv/bin/activatepip install -r requirements.txtcp .env.example .envnano .env(replace placeholders with real values)
Once the virtual environment has been activated, start the Flask app by running python app.py. You will also need to start an Ngrok session by running `ngrok http 5000 if your host does not have a public IP.
Once started, update the Twilio phone number, SIP Domain or TwiML App to the Ngrok URL or public IP/hostname. When a call comes in to Twilio, the Flask app will return standard TwiML to <Dial> the <Number> from the .env file. This will be a regular bridged call. To convert the bridged call to a conference, run python convert.py. The conversion script makes the assumption that there is only 1 active bridged call (with 2 call legs/SIDs) and as such, converts the latest call (the child call) to <Dial> a <Conference>. The conference name will be the parent Call SID (since SIDs are unique). The action URL will also return TwiML instructions to the parent call to join the same conference.
<Number> and <Conference> status callbacks have also been implemented for debugging purposes.
As previously mentioned, this script is designed to run in a dev/lab environment where only 1 call at a time takes place. This is due to the conversion script simply updating the latest call from the /Calls REST API. In a production environment, the conversion initiation could take place from a Web UI that targets a specific Call SID/child call.