RTL.ClassicBluetooth Sample

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Location

You can find the Classic Bluetooth Basic app sample project at:

  • Start | Programs | Embarcadero RAD Studio Athens | Samples and navigate to:
    • Object Pascal\Multi-Device Samples\Device Sensors and Services\Bluetooth\Classic Bluetooth Basic app
    • CPP\Multi-Device Samples\Device Sensors and Services\Bluetooth\Classic Bluetooth Basic app
  • Subversion Repository:
    • You can find Delphi and C++ code samples in GitHub Repositories. Search by name into the samples repositories according to your RAD Studio version.

Description

Note: This sample application does not work on iOS devices. For more information about platform support, see Using Classic Bluetooth.

This sample provides a FireMonkey application that is based on TTabControl with two different TTabItem: Bluetooth settings and Service demo.

You need another device that supports Classic Bluetooth to use this sample. You can try the functionality of a simple text service presented in the Service demo tab only if you install this sample on another device.

Bluetooth settings

The Bluetooth settings TTabItem provides options for discovering, pairing/unpairing devices and displaying services available on the paired device.

  • The Labeldiscoverable control shows the name under which other devices can see your device.
  • Discover devices: The ButtonDiscover control fires the ButtonDiscoverClick event handler.
  • Pair: The ButtonPair control fires the ButtonPairClick event handler.
  • UnPair: The ButtonUnPair control fires the ButtonUnPairClick event handler.
  • The ComboBoxDevices control allows you to choose a device from the list of discovered devices.
  • Paired Devices: The ButtonPairedDevices control fires the ButtonPairedDeviceClick event handler.
  • The ComboBoxPaired control allows you to choose a device from a list of paired devices. If there are any paired devices when you start the application, the first device on the list is automatically chosen.
  • Services: The ButtonServices control fires the ButtonServicesClick event handler.
  • The ComboBoxServices control allows you to choose a service from a list of available services.
  • The DisplayR control shows text output from the application, such as feedback on button clicks or errors that occur.

Service demo

The Service demo TTabItem provides both server and client functionality for a simple text service.

  • Create text service: The ButtonOpenReadingSocket control fires the ButtonOpenReadingSocketClick event handler.
  • Remove text service: The ButtonCloseReadingSocket control fires the ButtonCloseReadingSocketClick event handler.
  • Send text to->: The ButtonConnectToRFCOMM control fires the ButtonConnectToRFCOMMClick event handler.
  • The LabelNameSarver displays the name of the device that you selected from the list of paired devices.
  • The Edit1 control allows you to modify the text that you send to the other device (default is "I am the text sent").
  • Clear: The Button2 control fires the Button2Click event handler.
  • Free Client Socket: The FreeSocket control fires the FreeSocketClick event handler.
  • The DisplayR control shows text output from the application, such as feedback on button clicks or errors that occur.

How to Use the Sample

  1. Navigate to the location given above and open:
    • Delphi: ClBluetooth.dproj.
    • C++: ClBluetoothCpp.cbproj.
  2. As a target platform, select a device that supports Classic Bluetooth.
    Note: For more information about client platform support on Classic Bluetooth, see Using Classic Bluetooth.
  3. Press F9 or choose Run > Run.
  4. Discover devices.
  5. Choose a device from the list of discovered devices.
  6. Pair with that device.
    Note: On Android, after you successfully pair two devices you need to force-close (close in task manager) the application and reopen it. The paired device will then show in the list of paired devices. Pairing is not supported on Android lower than 4.4. To use this application on a device that has a lower version of Android, pair the devices using native system functionality and then run the sample application.
  7. See the services available on the paired device.
    Note: Devices with Android system version lower than 4.0.3. do not support this functionality.
  8. Unpair from a device (not supported on Android).

To try the functionality of the simple text service presented in the Service demo tab, you need to install this sample on another device. Follow the steps 1-6 from above on the second device and then:

  1. Choose the Service demo tab.
  2. Create a text service (on one or both of the devices).
  3. Send text from one device to the other (the receiving device needs to have a previously-created text service).
    Note: In C++ version, you need to free the client socket before sending the text (if you do not, the "Broken pipe" error will show).
  4. You can remove the text service and create it again.
    Note: In Delphi version, creating the text service after removing it has no effect. If you remove the text service you need to close the application and reopen it in order to use the text service.

Implementation

On initialization, the FormShow procedure creates a reference of the current Bluetooth manager and its adapter. If it successfully connects to the manager, it updates the ComboBoxPaired with the list of paired devices and displays the name of your device in the Labeldiscoverable control. If you run the sample application on an unsupported device or with the Bluetooth module turned off, FormShow shows the following exception in an alert: "Bluetooth device not found: disconnected or turned off".

TForm1

  • The application defines the following event handlers:
    • ButtonPairClick calls the Pair method of the current adapter. The parameter it passes, is the device that you select from the list of discovered devices. If you do not select a device, the event handler displays an alert: "No device selected".
    • ButtonUnPairClick calls the UnPair method of the current adapter. The parameter it passes, is the device that you select from the list of paired devices. If you do not select a device, the event handler displays an alert: "No Paired device selected".
    • ComboBoxPairedChange occurs every time the list of paired devices is updated. ComboBoxPairedChange updates the value displayed in the LabelNameSarver on the Service Demo tab with the name of the selected device from the list of paired devices.
    • ButtonPairedDeviceClick calls PairedDevices and opens the ComboboxPaired control.
    • ButtonServicesClick clears the ComboBoxServices control, adds the names of services available on the device you selected from the list of paired devices to the ComboBoxServices control and opens the ComboBoxServices control. If you do not select a device, the event handler displays an alert: "No paired device selected".
    • FreeSocketClick frees the instance of TBluetoothSocket that you initialize the first time you send text in the Service demo tab and displays the message "Client socket set free" in the DisplayR control. This method allows you to solve the problem where you cannot send the text to a device after removing and creating a text service on that device, because the client socket is still connected to the previous service.
    • Button2Click clears all the text in the DisplayR control.
    • ButtonConnectToRFCOMMClick calls SendData that tries to send the text in the Edit1 control to the device that you select from the list of paired devices. If you do not select a device, ButtonConnectToRFCOMMClick displays the exception "Argument out of range" in the DisplayR control. If the paired device that you send the text to does not have a text service running, ButtonConnectToRFCOMMClick displays the exception "IOException: read failed, socket might closed, read ret: -1" in the DisplayR control. If the paired device, that you send the text to, removes the text service and creates a new one, ButtonConnectToRFCOMMClick displays the exception "IOException: Broken pipe" in the DisplayR control. You can solve this problem by using the "Free Client Socket" functionality on the sending device.
    • ButtonDiscoverClick clears the ComboboxDevices control and starts a discovery with a timeout of 10 seconds. ButtonDiscoverClick also assignes the DevicesDiscoveryEnd event handler to the OnDiscoveryEnd event of the manager.
    • DevicesDiscoveryEnd handles the OnDiscoveryEnd event of the manager. DevicesDiscoveryEnd adds the names of discovered devices to the ComboboxDevices controls and selects the first device.
    • ButtonOpenReadingSocketClick calls TServerConnectionTH.Create to initialize an instance of the TServerConnectionTH class. Then ButtonOpenReadingSocketClick creates a server socket for that instance and calls TServerConnectionTH.Start to start the server thread. Finally, ButtonOpenReadingSocketClick displays a message in the DisplayR control: " - Service created: <ServiceName>". If you start the application on an unsupported device or with the Bluetooth module turned off, ButtonOpenReadingSocketClick displays the exception "No Bluetooth device found" in the DisplayR control.
    • ButtonCloseReadingSocketClick calls TServerConnectionTH.Terminate and TServerConnectionTH.WaitFor and then frees the instance of TServerConnectionTH that was created in ButtonOpenReadingSocketClick. Finally, ButtonCloseReadingSocketClick displays a message in the DisplayR control: " - Service removed -".
  • The application also defines the following methods:
    • PairedDevices clears the ComboboxPaired control and adds the names of the paired devices of the current manager to the ComboboxPaired control. If there are no paired devices, PairedDevices displays a message "No Paired Devices" in the DisplayR control.
    • GetServiceName accepts a Bluetooth service GUID as a parameter and returns the name of the corresponding Bluetooth service.
    • ManagerConnected returns True if the connection state of the manager is Connected and sets the text of Labeldiscoverable to "Device discoverable as <CurrentAdapter.AdapterName>". If the connection state is False it displays a message "No Bluetooth device found" in the DisplayR control and returns False.
    • SendData converts the text in the Edit1 control into bytes and sends them to the device you selected from the list of paired devices. If the client socket instance is nil, SendData calls CreateClientSocket. If the socket creation fails, SendData displays an alert "Out of time -15s-". If you did not select a device from the list of paired devices, SendData displays an alert "No paired device selected". If SendData sucessfully sends the text, it displays a message "Text Sent" in the DisplayR control.

TServerConnectionTH

This application implements a class TServerConnectionTH that is a subclass of TThread. This class provides the methods that support the server-side functionality of the text service on the Service demo tab.

  • TServerConnectionTH defines the following methods:
    • Create is the constructor.
    • Destroy is the destructor that frees the client socket and the server socket instance of this class.
    • execute is the implementation of the Execute method that runs when the thread is run. execute listens for incoming data on the instance of the server socket. When the data arrives, execute converts that data into a string and displays it in the DisplayR control. If the connected client device frees its socket, execute displays the exception "Server Socket closed: Channel is closed, cannot read data" in the DisplayR control.

Uses

See Also

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