The main function of the Bluetooth is a Bluetooth protocol stack. It defines and
provides different types of layers and functionalities. Bluetooth can run different application over
different protocol stacks, but, each one of these protocol stacks uses the same Bluetooth link and
physical layers. The diagram shows a complete Bluetooth protocol stack. It shows the relationship
between the protocols that use the services of other protocols when there is a payload to be
transferred in the air. Anyhow, the protocols have many other relationship between the other
protocols – for example, some protocols (L2CAP, TCS Binary) use the LMP to control the link manager.
This article describes how to use Bluetooth Framework with
Classic Bluetooth RFCOMM Protocol.
Table Of Contents
Bluetooth Framework and RFCOMM
The Bluetooth RFCOMM protocol is a simple set of transport protocols, made on top of the L2CAP protocol, providing emulated RS-232 serial ports. You usually know RFCOMM as Serial Port Profile (SPP). But that is not true at all. Serial Port Profile is just one of many profiles that are based on Bluetooth RFCOMM protocol. Object Push Profile (OPP), File Transfer Profile (FTP) and many others Bluetooth profiles work above RFCOMM (use RFCOMM as transport protocol).
Bluetooth Framework natively supports Bluetooth Classic RFCOMM protocol in client and server modes. That means that Bluetooth Framework can act as RFCOMM client (connects to other Bluetooth enabled devices) or as RFCOMM server (accepts connection from other Bluetooth enabled devices). That also means that you do not need to create and/or use any virtual COM ports to be able to communicate with Bluetooth enabled devices.
Bluetooth Profiles (Services)
In order to use Bluetooth technology, a device must be compatible with the subset of Bluetooth profiles (often called services). A Bluetooth profile (service) is a specification regarding an aspect of Bluetooth-based wireless communication between devices.
The way a device uses Bluetooth technology depends on its profile capabilities. The profiles provide standards which manufacturers follow to allow devices to use Bluetooth in the intended manner. Each Bluetooth profile built on-top of Bluetooth protocol. Bluetooth Framework can work only with profiles that built on-top of RFCOMM protocol. There are few exceptions but those exceptions are not a part of this article.
Bluetooth profile is defined by something known as Universally Unique ID (UUID). UUID is an abbreviation you will see a lot in the Bluetooth world. This service's UUID tells to toher device which Bluetooth features device supports. RFCOMM connection usually established with using service's UUID.
Bluetooth enabled device may query other Bluetooth enabled device device about supported service by sending request to its Service Discovering Protocol (SDP) service. In Bluetooth Framework you can do it by calling EnumRemoteServices() function.
procedure TfmMain.btEnumServicesClick(Sender: TObject);
var
Item: TListItem;
Radio: TwclBluetoothRadio;
Address: Int64;
Res: Integer;
Services: TwclBluetoothServices;
i: Integer;
begin
if lvDevices.Selected = nil then
MessageDlg('Select device', mtWarning, [mbOK], 0)
else begin
ClearServices;
Item := lvDevices.Selected;
Radio := TwclBluetoothRadio(Item.Data);
Address := StrToInt64('$' + Item.SubItems[0]);
Res := Radio.EnumRemoteServices(Address, nil, Services);
if Res <> WCL_E_SUCCESS then
ShowError(Res)
else begin
if Services <> nil then begin
try
for i := 0 to Length(Services) - 1 do begin
Item := lvServices.Items.Add;
Item.Caption := Radio.ApiName;
Item.SubItems.Add(IntToHex(Address, 12));
Item.SubItems.Add(IntToHex(Services[i].Handle, 8));
Item.SubItems.Add(GUIDToString(Services[i].Uuid));
Item.SubItems.Add(IntToStr(Services[i].Channel));
Item.SubItems.Add(Services[i].Name);
Item.SubItems.Add(Services[i].Comment);
end;
finally
Services := nil;
end;
end;
end;
end;
end;
void __fastcall TfmMain::btEnumServicesClick(TObject *Sender)
{
if (lvDevices->Selected == NULL)
MessageDlg("Select device", mtWarning, TMsgDlgButtons() << mbOK, 0);
else
{
ClearServices();
TListItem* Item = lvDevices->Selected;
TwclBluetoothRadio* Radio = (TwclBluetoothRadio*)Item->Data;
__int64 Address = StrToInt64("$" + Item->SubItems->Strings[0]);
TwclBluetoothServices Services;
int Res = Radio->EnumRemoteServices(Address, NULL, Services);
if (Res != WCL_E_SUCCESS)
ShowError(Res);
else
{
for (int i = 0; i < Services.Length; i++)
{
Item = lvServices->Items->Add();
Item->Caption = Radio->ApiName;
Item->SubItems->Add(IntToHex(Address, 12));
Item->SubItems->Add(IntToHex((int)Services[i].Handle, 8));
Item->SubItems->Add(Sysutils::GUIDToString(Services[i].Uuid));
Item->SubItems->Add(IntToStr(Services[i].Channel));
Item->SubItems->Add(Services[i].Name);
Item->SubItems->Add(Services[i].Comment);
}
}
}
}
private void btEnumServices_Click(object sender, EventArgs e)
{
if (lvDevices.SelectedItems.Count == 0)
MessageBox.Show("Select device", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning);
else
{
ClearServices();
ListViewItem Item = lvDevices.SelectedItems[0];
wclBluetoothRadio Radio = (wclBluetoothRadio)Item.Tag;
Int64 Address = Convert.ToInt64(Item.SubItems[1].Text, 16);
wclBluetoothService[] Services;
Guid g = Guid.Empty;
Int32 Res = Radio.EnumRemoteServices(Address, g, out Services);
if (Res != wclErrors.WCL_E_SUCCESS)
ShowError(Res);
else
{
if (Services != null)
{
try
{
foreach(wclBluetoothService Service in Services)
{
Item = lvServices.Items.Add(Radio.ApiName);
Item.SubItems.Add(Address.ToString("X12"));
Item.SubItems.Add(Service.Handle.ToString("X8"));
Item.SubItems.Add(Service.Uuid.ToString());
Item.SubItems.Add(Service.Channel.ToString());
Item.SubItems.Add(Service.Name);
Item.SubItems.Add(Service.Comment);
}
}
finally
{
Services = null;
}
}
}
}
}
Private Sub btEnumServices_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btEnumServices.Click
If lvDevices.SelectedItems.Count = 0 Then
MessageBox.Show("Select device", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning)
Else
ClearServices()
Dim Item As ListViewItem = lvDevices.SelectedItems(0)
Dim Radio As wclBluetoothRadio = CType(Item.Tag, wclBluetoothRadio)
Dim Address As Int64 = Convert.ToInt64(Item.SubItems(1).Text, 16)
Dim Services() As wclBluetoothService = Nothing
Dim g As Guid = Guid.Empty
Dim Res As Int32 = Radio.EnumRemoteServices(Address, g, Services)
If Res <> wclErrors.WCL_E_SUCCESS Then
ShowError(Res)
Else
If Services IsNot Nothing Then
Try
For Each Service As wclBluetoothService In Services
Item = lvServices.Items.Add(Radio.ApiName)
Item.SubItems.Add(Address.ToString("X12"))
Item.SubItems.Add(Service.Handle.ToString("X8"))
Item.SubItems.Add(Service.Uuid.ToString())
Item.SubItems.Add(Service.Channel.ToString())
Item.SubItems.Add(Service.Name)
Item.SubItems.Add(Service.Comment)
Next Service
Finally
Services = Nothing
End Try
End If
End If
End If
End Sub
void CBluetoothManagerDlg::OnBnClickedButtonEnumServices()
{
POSITION Pos = lvDevices.GetFirstSelectedItemPosition();
if (Pos == NULL)
AfxMessageBox(_T("Select device"));
else
{
ClearServices();
int Item = lvDevices.GetNextSelectedItem(Pos);
CwclBluetoothRadio* Radio = (CwclBluetoothRadio*)lvDevices.GetItemData(Item);
__int64 Address = StrToInt64(lvDevices.GetItemText(Item, 1));
wclBluetoothServices Services;
int Res = Radio->EnumRemoteServices(Address, NULL, Services);
if (Res != WCL_E_SUCCESS)
ShowError(Res);
else
{
if (Services.size() > 0)
{
try
{
int ndx = 0;
for (wclBluetoothServices::iterator i = Services.begin(); i != Services.end(); i++)
{
LPOLESTR Guid;
StringFromCLSID((*i).Uuid, &Guid);
lvServices.InsertItem(ndx, Radio->GetApiName().c_str());
lvServices.SetItemText(ndx, 1, IntToHex(Address));
lvServices.SetItemText(ndx, 2, IntToHex((int)(*i).Handle));
lvServices.SetItemText(ndx, 3, Guid);
lvServices.SetItemText(ndx, 4, IntToStr((*i).Channel));
lvServices.SetItemText(ndx, 5, (*i).Name.c_str());
lvServices.SetItemText(ndx, 6, (*i).Comment.c_str());
CoTaskMemFree(Guid);
ndx++;
}
}
finally(
Services.clear();
)
}
{
}
}
Bluetooth Framework uses wclBluetoothService structure to describe Bluetooth service information (it is also called Bluetooth Service Record or SDP Record) received from a remote Bluetooth enabled device.
TwclBluetoothService = record
Handle: Cardinal;
Uuid: TGuid;
Channel: Byte;
Name: string;
Comment: string;
end;
public struct wclBluetoothService
{
public UInt32 Handle;
public Guid Uuid;
public Byte Channel;
public String Name;
public String Comment;
};
typedef struct
{
unsigned long Handle;
GUID Uuid;
unsigned char Channel;
tstring Name;
tstring Comment;
} wclBluetoothService;
- Handle - a Bluetooth service's handle. This is an internal field and usualy means nothing for an application;
- Uuid - a service's UUID, what we are looking for;
- Channel - an RFCOMM channel number (see below);
- Name - a service's name;
- Comment - a service's comment, may contains some additional information about service implementation details.
RFCOMM Channel Number
As described above, a Bluetooth Service UUID just describes some feature that is supported by a Bluetooth enabled device. It is something like TCP/IP service: HTTP, FTP, TelNet or others. You can connect to any Internet service by using its IP address and service. However, Bluetooth device may have few services with identical UUID. For example, a device may have two Serial Port Profile (SPP) services: one for configuration and other for communication. It is similar if an Internet server has two HTTP servers running: one is public and other is for administration.
And now we have a question: how a Bluetooth client device may select which service it wants to connect to? Again, refer to the Internet: there is something known as TCP/IP port. If an Interner server has two HTTP servers then one may run on standard HTTP port 80 and the other may run on port 8080. So when connecting to such server browser uses default port 80 when it specifies HTTP service in connection request. But we also may provide TCP/IP port (8080) and a Web browser connects to specified port.
The same appears when we connect to a Bluetooth RFCOMM service. But instead of port in the Bluetooth world it is called an RFCOMM channel number (the Channel field in the wclBluetoothService structure). Each RFCOMM service has its own unique RFCOMM channel number. This channel number can be hardcoded or can be dynamically assigned. But it is always unique in a device's services list.
When Bluetooth RFCOMM client connects to a remote Bluetooth RFCOMM server it always connects to an RFCOMM channel. If application does not provide a channel number in connection request, OS queries remote Bluetooth device about its services and tries to resolve the RFCOMM channel number by service's UUID. If there are two or more services with the same UUID OS uses first found randomly.
However, in case of few services with the same UUID an application may query device about supported service, find required one (by its name or comment) and provide RFCOMM channel number in connection request to connect to exactly required service. Or, if RFCOMM channel number is hardcoded on a device's side an application may simple provide the known RFCOMM channel number without quering device services.
When you run a Bluetooth RFCOMM server you also provides service's UUID and (if required) RFCOMM channel number. If (by default) an application does not provide a channel number (this is recomended way) an OS assigns it automaticaly. However an application can provide fixed RFCOMM channel number. But in this case server may not start if OS already uses this channel number. The RFCOMM channel number can be any from 1 to 31 (including both).
Bluetooth Framework as RFCOMM Client
Bluetooth Framework provide the wclRfCommClient class that allows to connect to a remote Bluetooth enabled device's RFCOMM based service. Each object of the wclRfCommClient class can connect to one remote Bluetooth enabled device's service. To connect to more than one Bluetooth device at the same time an application must use more than one object of the wclRfCommClient class. The code below shows how to start connection.
procedure TfmMain.btConnectClick(Sender: TObject);
var
Res: Integer;
Radio: TwclBluetoothRadio;
Services: TwclBluetoothServices;
Connect: Boolean;
i: Integer;
Service: TGUID;
begin
if lvDevices.Selected = nil then
MessageDlg('Select device', mtWarning, [mbOK], 0)
else begin
Radio := GetRadio;
if Radio <> nil then begin
wclRfCommClient.Address := StrToInt64('$' + lvDevices.Selected.Caption);
wclRfCommClient.Authentication := cbAuthentication.Checked;
wclRfCommClient.Encryption := cbEncryption.Checked;
wclRfCommClient.Timeout := StrToInt(edTimeout.Text);
wclRfCommClient.Channel := 0;
wclRfCommClient.Service := SerialPortServiceClass_UUID;
Connect := False;
if cbServiceName.Checked then begin
Service := wclRfCommClient.Service;
Res := Radio.EnumRemoteServices(wclRfCommClient.Address,
@Service, // We are looking for specified services only!
Services);
if Res <> WCL_E_SUCCESS then
MessageDlg('Service enumerating error: 0x' + IntToHex(Res, 8), mtError, [mbOK], 0)
else begin
if Length(Services) = 0 then
ShowMessage('Services not found')
else begin
for i := 0 to Length(Services) - 1 do begin
if Services[i].Name = edServiceName.Text then begin
wclRfCommClient.Channel := Services[i].Channel;
Connect := True;
Break;
end;
end;
if not Connect then
ShowMessage('Service not found');
end;
end;
end else
Connect := True;
if Connect then begin
Res := wclRfCommClient.Connect(Radio);
if Res <> WCL_E_SUCCESS then
MessageDlg('Error: 0x' + IntToHex(Res, 8), mtError, [mbOK], 0)
end;
end;
end;
end;
void __fastcall TfmMain::btConnectClick(TObject *Sender)
{
if (lvDevices->Selected == NULL)
MessageDlg("Select device", mtWarning, TMsgDlgButtons() << mbOK, 0);
else
{
TwclBluetoothRadio* Radio = GetRadio();
if (Radio != NULL)
{
wclRfCommClient->Address = StrToInt64("$" + lvDevices->Selected->Caption);
wclRfCommClient->Authentication = cbAuthentication->Checked;
wclRfCommClient->Encryption = cbEncryption->Checked;
wclRfCommClient->Timeout = StrToInt(edTimeout->Text);
wclRfCommClient->Channel = 0;
wclRfCommClient->Service = SerialPortServiceClass_UUID;
bool Connect = false;
if (cbServiceName->Checked)
{
TwclBluetoothServices Services;
TGUID Service = wclRfCommClient->Service;
int Res = Radio->EnumRemoteServices(wclRfCommClient->Address,
&Service, // We are looking for specified services only!
Services);
if (Res != WCL_E_SUCCESS)
MessageDlg("Service enumerating error: 0x" + IntToHex(Res, 8), mtError, TMsgDlgButtons() << mbOK, 0);
else
{
if (Services.Length == 0)
ShowMessage("Services not found");
else
{
for (int i = 0; i < Services.Length; i++)
{
if (Services[i].Name == edServiceName->Text)
{
wclRfCommClient->Channel = Services[i].Channel;
Connect = true;
break;
}
}
if (!Connect)
ShowMessage("Service not found");
}
}
}
else
Connect = true;
if (Connect)
{
int Res = wclRfCommClient->Connect(Radio);
if (Res != WCL_E_SUCCESS)
MessageDlg("Error: 0x" + IntToHex(Res, 8), mtError, TMsgDlgButtons() << mbOK, 0);
}
}
}
}
private void btConnect_Click(object sender, EventArgs e)
{
if (lvDevices.SelectedItems.Count == 0)
MessageBox.Show("Select device", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning);
else
{
wclBluetoothRadio Radio = GetRadio();
if (Radio != null)
{
Client.Address = Convert.ToInt64(lvDevices.SelectedItems[0].Text, 16);
Client.Authentication = cbAuthentication.Checked;
Client.Encryption = cbEncryption.Checked;
Client.Timeout = (UInt32)Convert.ToInt32(edTimeout.Text);
Client.Channel = 0;
Client.Service = wclUUIDs.SerialPortServiceClass_UUID;
Boolean Connect = false;
if (cbServiceName.Checked)
{
Guid Service = Client.Service;
wclBluetoothService[] Services;
Int32 Res = Radio.EnumRemoteServices(Client.Address,
Service, // We are looking for specified services only!
out Services);
if (Res != wclErrors.WCL_E_SUCCESS)
MessageBox.Show("Service enumerating error: 0x" + Res.ToString("X8"));
else
{
if (Services == null || Services.Length == 0)
MessageBox.Show("Services not found");
else
{
foreach (wclBluetoothService s in Services)
{
if (s.Name == edServiceName.Text)
{
Client.Channel = s.Channel;
Connect = true;
break;
}
}
if (!Connect)
MessageBox.Show("Service not found");
}
}
}
else
Connect = true;
if (Connect)
{
Int32 Res = Client.Connect(Radio);
if (Res != wclErrors.WCL_E_SUCCESS)
MessageBox.Show("Error: 0x" + Res.ToString("X8"), "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
}
}
Private Sub btConnect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btConnect.Click
If lvDevices.SelectedItems.Count = 0 Then
MessageBox.Show("Select device", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning)
Else
Dim Radio As wclBluetoothRadio = GetRadio()
If Radio IsNot Nothing Then
Client.Address = Convert.ToInt64(lvDevices.SelectedItems(0).Text, 16)
Client.Authentication = cbAuthentication.Checked
Client.Encryption = cbEncryption.Checked
Client.Timeout = Convert.ToInt32(edTimeout.Text)
Client.Channel = 0
Client.Service = wclUUIDs.SerialPortServiceClass_UUID
Dim Connect As Boolean = False
If cbServiceName.Checked Then
Dim Service As Guid = Client.Service
Dim Services As wclBluetoothService()
Dim Res As Int32 = Radio.EnumRemoteServices(Client.Address, Service, Services)
If Res <> wclErrors.WCL_E_SUCCESS Then
MessageBox.Show("Service enumerating error: 0x" + Res.ToString("X8"))
Else
If Services Is Nothing Or Services.Length = 0 Then
MessageBox.Show("Services not found")
Else
Dim s As wclBluetoothService
For Each s In Services
If s.Name = edServiceName.Text Then
Client.Channel = s.Channel
Connect = True
Exit For
End If
Next s
If Not Connect Then
MessageBox.Show("Service not found")
End If
End If
End If
Else
Connect = True
End If
If Connect Then
Dim Res As Int32 = Client.Connect(Radio)
If Res <> wclErrors.WCL_E_SUCCESS Then
MessageBox.Show("Error: 0x" + Res.ToString("X8"), "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End If
End If
End If
End If
End Sub
void CRfCommClientDlg::OnBnClickedButtonConnect()
{
POSITION Pos = lvDevices.GetFirstSelectedItemPosition();
if (Pos == NULL)
AfxMessageBox(_T("Select device"));
else
{
int Item = lvDevices.GetNextSelectedItem(Pos);
CwclBluetoothRadio* Radio = GetRadio();
if (Radio != NULL)
{
wclRfCommClient.SetAddress(StrToInt64(lvDevices.GetItemText(Item, 0)));
wclRfCommClient.SetAuthentication(cbAuthentication.GetCheck() != 0);
wclRfCommClient.SetEncryption(cbEncryption.GetCheck() != 0);
CString s;
edTimeout.GetWindowText(s);
wclRfCommClient.SetTimeout(StrToInt(s));
wclRfCommClient.SetChannel(0);
wclRfCommClient.SetService(SerialPortServiceClass_UUID);
bool Connect = false;
if (cbServiceName.GetCheck())
{
GUID Service = wclRfCommClient.GetService();
wclBluetoothServices Services;
int Res = Radio->EnumRemoteServices(wclRfCommClient.GetAddress(), &Service, Services);
if (Res != WCL_E_SUCCESS)
AfxMessageBox(_T("Service enumerating error: 0x") + IntToHex(Res));
else
{
if (Services.size() == 0)
AfxMessageBox(_T("Services not found"));
else
{
for (wclBluetoothServices::iterator s = Services.begin(); s != Services.end(); s++)
{
CString str;
edServiceName.GetWindowText(str);
tstring strs(str);
if ((*s).Name == strs)
{
wclRfCommClient.SetChannel((*s).Channel);
Connect = true;
break;
}
}
if (!Connect)
AfxMessageBox(_T("Service not found"));
}
}
}
else
Connect = true;
if (Connect)
{
int Res = wclRfCommClient.Connect(Radio);
if (Res != WCL_E_SUCCESS)
AfxMessageBox(_T("Error: 0x") + IntToHex(Res));
}
}
}
}
Once an application sets all required parameters (target device's address, service's UUID, RFCOMM channel number, Authentication and/or Encryption mode) an application calls the Connect() method that starts connection procedure. The only required parameter is a terget device's MAC address. By default wclRfCommClient connects to Serial Port Profile (SPP) with the authentication enabled and the encryption disabled. If the RFCOMM channel number (the Channel property) is not set or set to zero (the default value) the OS tries to resolve it using service's UUID as described above in the RFCOMM Channel Number section.
The Connect() method just starts connection procedure. The returning value just indicates (if success) that the connection procedure has been started. Or that the connection procedure has not been started (in case of error). When connection procedure is completed (connection is established or is not established) the OnConnect() event celled with the connection result code.
procedure TfmMain.wclRfCommClientConnect(Sender: TObject; const Error: Integer);
begin
if Error = WCL_E_SUCCESS then begin
lbEvents.Items.Add('Connected');
GetBuffers;
end else
lbEvents.Items.Add('Connect error: 0x' + IntToHex(Error, 8));
end;
void __fastcall TfmMain::wclRfCommClientConnect(TObject *Sender, const int Error)
{
if (Error == WCL_E_SUCCESS)
{
lbEvents->Items->Add("Connected");
GetBuffers();
}
else
lbEvents->Items->Add("Connect error: 0x" + IntToHex(Error, 8));
}
void Client_OnConnect(object Sender, int Error)
{
if (Error == wclErrors.WCL_E_SUCCESS)
{
lbEvents.Items.Add("Connected");
GetBuffers();
}
else
lbEvents.Items.Add("Connect error: 0x" + Error.ToString("X8"));
}
Private Sub Client_OnConnect(ByVal Sender As Object, ByVal [Error] As Integer) Handles Client.OnConnect
If [Error] = wclErrors.WCL_E_SUCCESS Then
lbEvents.Items.Add("Connected")
GetBuffers()
Else
lbEvents.Items.Add("Connect error: 0x" + [Error].ToString("X8"))
End If
End Sub
void CRfCommClientDlg::wclRfCommClientConnect(void* Sender, int Error)
{
if (Error == WCL_E_SUCCESS)
{
lbEvents.AddString(_T("Connected"));
GetBuffers();
}
else
lbEvents.AddString(_T("Connect error: 0x") + IntToHex(Error));
}
As you can see in the code above the real connection result is passed as the Error parameter into the OnConnect() event handler. If the Error parameter value is WCL_E_SUCCESS the connection to a remote device has been established with success. If the Error parameter has other value it indicates one of the connection error code (you can find list of all Wireless Communication Library error codes by this link).
Once connection is established an application can start communication with a connected Bluetooth device. To send data to the connected device an application calls the Write() method of the wclRfCommClient class.
procedure TfmMain.btSendClick(Sender: TObject);
var
Ansi: AnsiString;
Res: Integer;
Sent: Cardinal;
begin
Ansi := AnsiString(edText.Text);
Res := wclRfCommClient.Write(PByte(Ansi), Length(Ansi), Sent);
if Res <> WCL_E_SUCCESS then
MessageDlg('Error: 0x' + IntToHex(Res, 8), mtError, [mbOK], 0)
else
MessageDlg('Sent: ' + IntToStr(Sent) + ' from ' + IntToStr(Length(Ansi)), mtInformation, [mbOK], 0);
end;
void __fastcall TfmMain::btSendClick(TObject *Sender)
{
AnsiString Ansi = AnsiString(edText->Text);
unsigned int Sent = 0;
int Res = wclRfCommClient->Write(Ansi.c_str(), Ansi.Length(), Sent);
if (Res != WCL_E_SUCCESS)
MessageDlg("Error: 0x" + IntToHex(Res, 8), mtError, TMsgDlgButtons() << mbOK, 0);
else
MessageDlg("Sent: " + IntToStr((int)Sent) + " from " + IntToStr(Ansi.Length()), mtInformation, TMsgDlgButtons() << mbOK, 0);
}
private void btSend_Click(object sender, EventArgs e)
{
Byte[] Ansi = Encoding.ASCII.GetBytes(edText.Text);
UInt32 Sent = 0;
Int32 Res = Client.Write(Ansi, out Sent);
if (Res != wclErrors.WCL_E_SUCCESS)
MessageBox.Show("Error: 0x" + Res.ToString("X8"));
else
MessageBox.Show("Sent: " + Sent.ToString() + " from " + Ansi.Length.ToString());
}
Private Sub btSend_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btSend.Click
Dim Ansi As Byte() = System.Text.Encoding.ASCII.GetBytes(edText.Text)
Dim Sent As UInt32 = 0
Dim Res As Int32 = Client.Write(Ansi, Sent)
If Res <> wclErrors.WCL_E_SUCCESS Then
MessageBox.Show("Error: 0x" + Res.ToString("X8"))
Else
MessageBox.Show("Sent: " + Sent.ToString() + " from " + Ansi.Length.ToString())
End If
End Sub
void CRfCommClientDlg::OnBnClickedButtonSend()
{
CString s;
edText.GetWindowText(s);
CStringA Ansi(s);
unsigned long Sent;
int Res = wclRfCommClient.Write(Ansi.GetBuffer(), Ansi.GetLength(), Sent);
if (Res != WCL_E_SUCCESS)
AfxMessageBox(_T("Error: 0x") + IntToHex(Res));
else
AfxMessageBox(_T("Sent: ") + IntToStr(Sent) + _T(" from ") + IntToStr(Ansi.GetLength()));
}
When data received from the device the OnData() event called. That was the basic information you need to know about RFCOMM connection.
procedure TfmMain.wclRfCommClientData(Sender: TObject; const Data: Pointer; const Size: Cardinal);
var
Str: AnsiString;
begin
if Size > 0 then begin
SetLength(Str, Size);
CopyMemory(Pointer(Str), Data, Size);
lbEvents.Items.Add('Received: ' + string(Str));
end;
end;
void __fastcall TfmMain::wclRfCommClientData(TObject *Sender, const Pointer Data, const DWORD Size)
{
if (Size > 0)
{
AnsiString Str = AnsiString((AnsiChar*)Data, Size);
lbEvents->Items->Add("Received: " + String(Str));
}
}
void Client_OnData(object Sender, byte[] Data)
{
if (Data != null && Data.Length > 0)
{
String Str = Encoding.ASCII.GetString(Data);
lbEvents.Items.Add("Received " + Data.Length.ToString() + " bytes: " + Str);
}
}
Private Sub Client_OnData(ByVal Sender As Object, ByVal Data() As Byte) Handles Client.OnData
If Data IsNot Nothing And Data.Length > 0 Then
Dim Str As String = System.Text.Encoding.ASCII.GetString(Data)
lbEvents.Items.Add("Received: " + Str)
End If
End Sub
void CRfCommClientDlg::wclRfCommClientData(void* Sender, void* Data, unsigned long Size)
{
if (Size > 0)
{
CStringA Str((PCHAR)Data, (int)Size);
CString s(Str);
lbEvents.AddString(_T("Received: ") + s);
}
}
Demo Applications
Bluetooth Framework package includes the RfCommClient and RfCommServer demo applications. The first one shows how to you Bluetooth Framework as Bluetooth RFCOMM client. The second one shows how to switch your compunter into Bluetooth RFCOMM server.
To find out more details about discovering Bluetooth devices, pairing with required one and about how to enumerate services on a remote Bluetooth device refer to BluetoothManager demo application.
Note: the wclRfCommClient and wclRfCommServer demo applications use Serial Port Profile service and waits text on both sides. That means that the applications convert received data into text to be able to display it to the user.
Additional Resources
- Download Bluetooth Framework
- Bluetooth Framework and Bluetooth Low Energy GATT
- Wireless Communication Library error codes