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, on port 1, 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 when:

Blue Dot is released, pressed or moved - [0,1,2],[x],[y]\n:

  • client to server.

  • operation:

    1. Blue Dot released.
    2. Blue Dot pressed.
    3. Blue Dot pressed position moved.
  • x & y specify the position on the Blue Dot that was pressed, released, and/or moved:

    • Positions are values between -1 and +1, with 0 being the centre and 1 being the radius of the Blue Dot.
    • x is the horizontal position where +1 is far right.
    • y is the vertical position where +1 is the top.

At connection the client sends a handshake - [3],[protocol version],[client name]

  • client to server.
  • operation 3.
  • protocol version is sent and corresponds to the version of protocol the client supports.
  • client name is a string value used in exceptions to report what client has connected.

When the setup (or appearance) of the Blue Dot changes - [4],[color],[square],[border],[visible]:

  • server to client.
  • operation 4.
  • color is a hex value in the format #rrggbbaa representing red, green, blue, alpha values.
  • square is 0 or 1, 1 if the dot should be a square.
  • border is 0 or 1, 1 if the dot should have a border.
  • visible is 0 or 1, 1 if the dot should be visible.

\n represents the ASCII new-line character (ASCII character 10).


When the Android client connects using protocol version 1:

3,1,Android Blue Dot app\n

If the blue dot is pressed at the top, the following message will be sent:


While the blue dot 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 dot is changed to “red” the server sends to the client:


Protocol versions

  • 0 - initial version
  • 1 - introduction of operation 3, 4