Changing the Bluetooth Radio Mode

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Microsoft Windows Mobile provides the following APIs that enable you to change the Bluetooth power status on a local device.

The supported power states for Bluetooth are as follows:

  • Power off

    Bluetooth is turned off on the device.

  • Connectable

    Bluetooth is turned on. The local device can initiate a connection with a peer device but the local device is not discoverable by peer devices that are within range.

  • Discoverable

    Bluetooth is turned on. The local device is listed, when a peer device searches for available devices within range. The peer device can pair with the local device.

    Security Note   Turn off Bluetooth after data transfer is complete. Enable Discoverable mode only when required. Use a different passcode for the pairing process each time.

These values are defined in the BTH_RADIO_MODE enumeration.

Sample Code

The following code example shows how to change the Bluetooth radio state.


  DWORD dwMode;
  WCHAR szMessage[50];
  iResult = BthGetMode(&dwMode);
  StringCchPrintf( szMessage, sizeof(szMessage), L"Current mode: %x. Change state? ", dwMode);
  if (MessageBox(NULL, szMessage, L"Info", MB_YESNO) == IDYES)
    if (dwMode == BTH_POWER_OFF )

    StringCchPrintf( szMessage, sizeof(szMessage), L"Status changed. \n Current Status: %x", dwMode);
    MessageBox(NULL, szMessage, L"Info", MB_OK);


using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using System.Collections.Generic;
using System.Text;

namespace BthToggleRadio
  class BthRadio
    public enum  RadioMode
      Off = 0,
      Connectable = 1,
      Discoverable =2

    [DllImport ("BthUtil.dll")]
    public static extern int BthGetMode (out RadioMode dwMode);

    public static extern int BthSetMode(RadioMode dwMode);

    public static void Main()
      RadioMode mode=RadioMode.Off;
      int ret = 0;
      ret=BthGetMode (out mode);
      DialogResult resDlg;
      resDlg=MessageBox.Show("Current mode: " + mode.ToString() + "\n" + "Change status?", "Bluetooth Status", MessageBoxButtons .YesNo, MessageBoxIcon.None, MessageBoxDefaultButton.Button1);
      if (resDlg == DialogResult.Yes)
          if (mode == RadioMode.Off)
          ret = BthSetMode(RadioMode.Discoverable);
            ret = BthSetMode(RadioMode.Off);
        ret = BthGetMode(out mode);
        resDlg = MessageBox.Show("Status changed. \n" + "Current Status: " + mode.ToString(), "Bluetooth Status");

[Visual Basic]

Imports System
Imports System.Runtime.InteropServices
Imports System.Windows.Forms

Class BthRadio
    Public Enum RadioMode
        RadioOff = 0
        Connectable = 1
        Discoverable = 2
    End Enum 'RadioMode 
    Public Declare Function BthGetMode Lib "BthUtil.dll" (ByRef dwMode As RadioMode) As Integer    
    Public Declare Function BthSetMode Lib "BthUtil.dll" (ByVal dwMode As RadioMode) As Integer        
    Public Shared Sub Main() 
        Dim mode As RadioMode = RadioMode.RadioOff 
        Dim ret As Integer = 0
        ret = BthGetMode(mode)
        Dim resDlg As DialogResult
        resDlg = MessageBox.Show("Current mode: " + mode.ToString() + vbLf + "Change status?", "Bluetooth Status", MessageBoxButtons.YesNo, MessageBoxIcon.None, MessageBoxDefaultButton.Button1)
        If resDlg = DialogResult.Yes Then
            If mode = RadioMode.RadioOff  Then
                ret = BthSetMode(RadioMode.Discoverable)
                ret = BthSetMode(RadioMode.RadioOff )
            End If
            ret = BthGetMode(mode)
            resDlg = MessageBox.Show("Status changed. " + vbLf + "Current Status: " + mode.ToString(), "Bluetooth Status")
        End If
    End Sub 'Main
End Class 'BthRadio 

See Also

Bluetooth Application Development for Windows Mobile-based Devices

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