linux-bluetoothctl-dbus-nodejs - OTTStreamingVideo.net

README.md

Subject: Bluetooth and D-Bus Tool for Linux

Date: 05-05-2022

License: This software is provided free of charge in accordance with GNU General Public License version 3.

Support: This software is provided without any warranty or guarantee of any kind, and without any promise of support.

Note: This software was written on an Ubuntu 22.04 desktop workstation and may also operate on other Linux distributions (e.g. Debian and Raspberry Pi OS).

Overview

For a detailed explaination of how bluetooth operates in Linux, please download the study guide.

This tool provides a method to interact with the Linux bluetoothctl and dbus functions in NodeJs by spawning bash shells as child processes.

This tool is intended for development use on a single computer and does not include the normal public web security functions such as:

firewall (e.g. ufw)
https SSL certificate (e.g. Let's Encrypt)
key file with password for secure SSH access
domain name

The web interface uses a very simple Single Page Architecture ("SPA") for the HOME and README (i.e. this file rendered as HTML) content areas.

Prerequistes

For Ubuntu 22.04, install NodeJS and NPM from the standard repositories:
```
 sudo apt install nodejs npm
```

Verify:

 node -v
 # expected version is 12.22.9 later

 npm -v
 # expected version is 8.5.1 or later

Earlier versions of NodeJS and NPM may likely operate also.

Installation

Choose your preferred installation directory (e.g. $HOME):
```
 cd ~
```

Clone the repository:

 git clone https://github.com/OTTStreamingVideo/linux-bluetoothctl-dbus-nodejs.git

Change directory to the repo directory:
```
 cd linux-bluetoothctl-dbus-nodejs
```

Install the required NodeJS packages:

 npm install ip
 npm install util
 npm install md5
 npm install https
 npm install url
 npm install body-parser
 npm install express
 npm install ws
 npm install markdown-it

Start the server.js app:

 node server.js
 # the shell terminal will display NodeJS console output

Open a web browser (e.g. Chrome, Chromium, Firefox, Opera):
```
 http://localhost:3000/
```
Click on the "bluetoothctl" and/or "dbus" button to see the bash shell outputs as they occur.
Modify the code as desired. Please fork the project and submit a pull request if you write code that could be useful to other developers.

PulseAudio and GStreamer

Bluetooth audio functions can be written with PulseAudio and Gstreamer.

In Ubuntu 22, you can see what PulseAudio packages are installed with:

    apt list --installed | grep pulse 
    # not all PulseAudio packages contain "pulse"

You can see what packages are available in the repository with:

    apt list | grep pulse
    # not all PulseAudio packages contain "pulse"

Some useful PulseAudio commands are:

    pactl list
    pactl list short

A very useful PulseAudio tool that is not installed in Ubuntu 22 desktop by default is pavacontrol.

In Ubuntu 22, you can see what GStreamer packages are installed with:

    apt list --installed | grep gst
    # not all GStreamer packages contain "gst"

You can see what packages are available in the repository with:

    apt list | grep gst
    # not all GStreamer packages contain "gst"

Some useful Gstreamer commands are:

    gst-inspect-1.0
    # with no argument all available elements and plugins are listed

    gst-discoverer-1.0 --help

    gst-launch-1.0 --help

Mobile Phone Bluetooth Experiment

Connect a mobile phone to your Ubuntu computer with the desktop Settings-Bluetooth control.
Monitor the dbus output for messages indicating that the phone has connected.
Call the connected mobile phone from a different mobile phone.
Monitor the dbus output for messages indicating that the phone call has been received.
View the Ubuntu Settings-Sound control (or pavucontrol) to see what bluetooth profile is in use (e.g. Headset Audio Gateway).

Execute a Gstreamer command to output audio from the bluetooth connection to a speaker attached to your Ubuntu desktop workstation, e.g.:

 GST_DEBUG=3 gst-launch-1.0 pulsesrc device=bluez_source.XX_XX_XX_XX_XX_XX.headset_audio_gateway volume=5.0 ! \
 queue ! \
 audioconvert ! \
 audioresample ! \
 pulsesink device=alsa_output.pci-0000_00_03.0.hdmi-stereo volume=5.0

 Note: use `pactl list` to find the pulsesrc device, and also to find the pulsesink device.

Write code to interact with the bluetoothctl and dbus that will execute your desired GStreaner audio functions.
```
 Note: You are responsible for the lawful and ethical use of audio recording and monitoring.
```