Blue Dot uses a client/server model. The BlueDot class starts a Bluetooth server, the Blue Dot application connects as a client.

The detail below can be used to create new applications (clients); if you do please send a pull request :)


Communication over Bluetooth is made using a RFCOMM serial port profile using UUID “00001101-0000-1000-8000-00805f9b34fb”.


The transmission of data from client to server or server to client is a simple stream no acknowledgements or data is sent in response to commands.

All messages between conform to the same format:


Messages are sent as utf-8 encoded strings.

\n represents the new-line character.

The following operations are used to communicate between client and server.

Operations Message format Direction
Button released 0,[col],[row],[x],[y]\n Client > Server
Button pressed 1,[col],[row],[x],[y]\n Client > Server
Button moved 2,[col],[row],[x],[y]\n Client > Server
Protocol check 3,[protocol version],[client name]\n Client > Server
Set config 4,[color],[square],[border],[visible],[cols],[rows]\n Server > Client
Set button config 5,[color],[square],[border],[visible],[col],[row]\n Server > Client

Messages are constructed using the following parameters.

Parameter Description
cols The number of columns in the matrix of buttons
rows The number of rows in the matrix of buttons
col The column position of the button (0 is top)
row The row position of the button (0 is left)
x Horizontal position between -1 and +1, with 0 being the centre and +1 being the right radius of the button.
y Vertical position between -1 and +1, with 0 being the centre and +1 being the top radius of the button.
protocol version The version of protocol the client supports.
client name The name of the client e.g. “Android Blue Dot App”
color A hex value in the format #rrggbbaa representing red, green, blue, alpha values.
square 0 or 1, 1 if the dot should be a square.
border 0 or 1, 1 if the dot should have a border.
visible 0 or 1, 1 if the dot should be visible.

Messages are sent when:

  1. A client connects
  2. When the setup (or appearance) of a button changes
  3. A button is released, pressed or moved
Diagram showing the protocol states


When the Android client connects using protocol version 2:

3,2,Android Blue Dot app\n

The setup of the Blue Dot is sent to the client:


If any buttons are different to the default, the configuration is sent:


If the “first” button at position [0,0] is pressed at the top, the following message will be sent:


While the button is pressed (held down), the user moves their finger to the far right causing the following message to be sent:


The button is then released, resulting in the following message:


The color of the button is changed to “red” the server sends to the client:



  • 0 - initial version
  • 1 - introduction of operation 3, 4
  • 2 - Blue Dot version 2, introduction of col, row for multiple buttons and operation 5