Connect to bluetooth device from command line

Question

Background: I'm using my bluetooth headset as audio output. I managed to get it working by the long list of instructions on BluetoothHeadset community documentation, and I have automated the process of activating the headset as default audio output into a script, thanks to another question.

However, since I use the bluetooth headset with both my phone and computer (and the headset doesn't support two input connections) in order for the phone not to "steal" the connection when handset is turned on, I force the headset into a discovery mode when connecting to the computer (phone gets to connect to it automatically).

So even though the headset is paired ok and would in "normal" scenario autoconnect, I have to always use the little bluetooth icon in the notification area to actually connect to my device (see screenshot).

What I want to avoid: This GUI for connecting to a known and paired bluetooth device:

What I want instead: I'd want to make the bluetooth do exactly what the clicking the connect item in the GUI does, only by using command line. I want to use command line so I can make a single keypress shortcut for the action, and would't need to navigate the GUI every time I want to establish a connection to the device.

The question: How can I attempt to connect to a specific, known and paired bluetooth device from command line?

Further question: How do I tell if the connection was successful or not?

Answer 1

Bluetooth daemon

In the default installation a daemon (bluetoothd) runs in the background (run from the file /etc/init.d/bluetooth). This daemon takes care on recognizing and connecting to known bluetooth devices and may be cofigured with configuration files in /etc/bluetooth. For autoconneting a headset the following line in audio.conf should be uncommented (remove #):

AutoConnect=true

To restart the daemon type sudo /etc/init.d/bluetooth restart.

_{Remark: Using the command line tool sudo hcitool cc <MAC-Adress> did not lead to a stable connection to a known device in the test environment here when the daemon was running.}

---

DBus

In order to connect a disconnected but physically present and paired headset we can use D-Bus from a script. Here's an example in python:

#!/usr/bin/python
# Toggles headset connection

import dbus
from dbus.mainloop.glib import DBusGMainLoop

dbus_loop = DBusGMainLoop()
bus = dbus.SystemBus(mainloop=dbus_loop)

#Get dbus interface for headset
manager = bus.get_object('org.bluez', '/')
iface_m = dbus.Interface(manager, 'org.bluez.Manager')
adapterPath = iface_m.DefaultAdapter()
adapter = bus.get_object('org.bluez', adapterPath)
iface_a = dbus.Interface(adapter, 'org.bluez.Adapter')
devicePath = iface_a.ListDevices()[0]  # assuming first device
device = bus.get_object('org.bluez', devicePath)
iface_h = dbus.Interface(device, 'org.bluez.Headset')

#Check state of connection
connected = iface_h.IsConnected()
print 'Toggling connection. Please wait'
# toggle connection
if not connected:
    try:
        iface_h.Connect()
        print 'Connecting: ', devicePath
    except:
        print 'Device not found'
else:
    iface_h.Disconnect()
    print 'Disconnecting: ', devicePath

In case we have more than one Bluetooth device we will have to adapt the devicePath appropriately, of course. The example above will connect a Headset. Change the interface to a different protocol for any other service (e.g. AudioSink).

---

Pulseaudio

If you know the MAC adress of your Bluetooth device you can connect it as an output sink for pulseaudio by:

pacmd set-default-sink bluez_sink.xx_xx_xx_xx_xx_xx

Where xx_xx_xx_xx_xx_xx is the MAC address (replace ':' by '_' for pulseaudio to recognize it).

See also this answer for more details.

Answer 2

After trying some of the above (scripts didn't work for me) I found the following solution.

First find out the MAC-Adress of the device you want to connect to

bluetoothctl

this will enter a shell and list all available devices with adress. ("quit" to exit the shell & get back to prompt)

Then connect to XX:XX:XX:XX:XX:XX bluetooth device :

echo -e 'connect XX:XX:XX:XX:XX:XX' | bluetoothctl

to disconnect

echo -e 'disconnect XX:XX:XX:XX:XX:XX' | bluetoothctl

been searching for this quite a while - nothing seemed to work, felt so relieved when I found out. Thought others might want to know about it, too. :))

Answer 3

I use this script to connect my Bluetooth Audio Device. If your headset is already paired, you should be able to connect your headset in the same way using org.bluez.Headset.Connect/Disconnect in place of org.bluez.Audiosink.Connect/Disconnect.

#!/bin/bash

MAC_ADD="C8:84:47:10:11:CD"

MAC_ADD="dev_${MAC_ADD//:/_}"
BT_ADAPTER=`dbus-send --system --print-reply --dest=org.bluez / \
org.bluez.Manager.DefaultAdapter|awk '/object path/ {print $3}'`

BT_ADAPTER="${BT_ADAPTER//\"/}/$MAC_ADD"
echo "Connecting to $BT_ADAPTER..."

if [ "$1" == "on" ]; then
    dbus-send --print-reply --system --dest=org.bluez $BT_ADAPTER org.bluez.AudioSink.Connect
elif [ "$1" == "off" ]; then
    dbus-send --print-reply --system --dest=org.bluez $BT_ADAPTER org.bluez.AudioSink.Disconnect
fi

HTH!

Answer 4

I use i3 as a window manager so I do not have the bluetooth tray icon available. For some reason the check button in unity settings is not sensitive and so I need a way to do this from time to time when my headphones don't connect.

It seems that bluez has changed their dbus API. The answer utilizing org.bluez.Manager no longer appears to work. Instead, it is recommended to use ObjectManager.

Here is an updated python script which will connect the first unconnected bluetooth headset that it finds (presumably the list includes all paired devices?):

#!/usr/bin/env python
# Toggles headset connection

from __future__ import print_function
from __future__ import unicode_literals

import dbus
from dbus.mainloop.glib import DBusGMainLoop

def find_headset(bus):
  manager = dbus.Interface(bus.get_object("org.bluez", "/"),
                           "org.freedesktop.DBus.ObjectManager")
  objects = manager.GetManagedObjects()

  for path, ifaces in objects.items():
    if ("org.bluez.Device1" in ifaces and
        "org.freedesktop.DBus.Properties" in ifaces):
      iprops = dbus.Interface(
          bus.get_object("org.bluez", path),
          "org.freedesktop.DBus.Properties")
      props = iprops.GetAll("org.bluez.Device1")
      # Looking for a headset. Could also match on other properties like
      # "Name". See bluez docs for whats available.
      if props.get("Class") == 0x240404:
        if props.get("Connected"):
          print("Found headset {} ({}) but it is already connected"
                .format(props.get("Name"), props.get("Address")))
          continue
        return path

dbus_loop = DBusGMainLoop()
bus = dbus.SystemBus(mainloop=dbus_loop)
hpath = find_headset(bus)

if hpath:
  adapter = dbus.Interface(
      bus.get_object("org.bluez", hpath), "org.bluez.Device1")
  adapter.Connect()

this example, like the other example on this thread, uses the dbus python package. On ubuntu 16.04 I installed this through apt-get install python-dbus.

If you wish to match other criteria, this document appears to show a list of properties that can be queried over dbus.

I have this script saved in ~/.local/bin/bt-connect-headset which is on my PATH so I can execute it from the i3 launcher. Make it executable (chmod +x bt-connect-headset) if you plan to use it as a command.

This script has only been tested on an up-to-date ubuntu 16.04 as of 09/28/2018.