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Now that you have decided on the best method of selecting a remote device you will need to go through the process. For the purposes of this tutorial we will assume you are going to allow the program to determine the remote device with which to connect.
Each Bluetooth device has a 48-bit unique address built into its hardware. A basic inquiry for devices in range returns zero or more of these addresses.
As well as an address, a Bluetooth device has a text name suitable for display to users. If you want to display a list of available devices to the user, you will also need to obtain these names.
The address and the name inquiries can occur simultaneously, if the underlying hardware supports this. Otherwise, the address inquiry must finish before the name request can be issued over the air.
Address and name inquiries are performed through the generic Symbian OS
sockets class RHostResolver
. A specialist Bluetooth
sockets address class, TInquirySockAddr
, which
encapsulates Bluetooth address, Inquiry Access Code, and service and device
classes, is provided for use with such inquiries.
To inquire for the addresses of remote devices, take the following steps:
Connect to the Sockets Server (RSocketServ
),
and then select the protocol to be used using
RSocketServ::FindProtocol()
. Address and name queries are
supplied by the stack's BTLinkManager protocol layer, so select this.
Create and initialise an RHostResolver
object.
Set the TInquirySockAddr
parameter for the inquiry:
for address inquiries, the KHostResInquiry
flag must be
set through TInquirySockAddr::SetAction()
.
The query can then be started with
RHostResolver::GetByAddress()
.
When GetByAddress()
completes, it fills in a
TNameEntry
object with the address and class of the first
device found (or is undefined if no device was found).
To get all the devices discovered, call
RHostResolver::Next()
repeatedly until
KErrHostResNoMoreResults
is returned.
The following example shows how to start a remote device address inquiry.
Connect to the socket server
RSocketServ socketServ;
socketServ.Connect();
TProtocolDesc pInfo;
_LIT(KL2Cap, "BTLinkManager");
User::LeaveIfError(socketServ.FindProtocol(KL2Cap,pInfo));
Create and initialise an RHostResolver
RHostResolver hr;
User::LeaveIfError(hr.Open(socketServ,pInfo.iAddrFamily,pInfo.iProtocol));
Set up a discovery query and start it
TInquirySockAddr addr;
TNameEntry entry;
addr.SetIAC(KGIAC);
addr.SetAction(KHostResInquiry);
TRequestStatus status;
hr.GetByAddress(addr, entry, status);
User::WaitForRequest(status);
Process the information returned in entry
...
TInquirySockAddr::SetIAC()
sets the
Bluetooth Inquiry Access Code. For more information, see
Bluetooth Assigned
Numbers.
The host resolver caches the results of inquiries so that devices that are no longer present may appear in the list of results. This does not cause any additional complications, as it is always possible for a device to go out of range between when it is discovered and when a connection to it is made.
Communications API calls are typically asynchronous (indicated by
a TRequestStatus
parameter in the call). It is recommended
that such calls are encapsulated in active objects, as explained in
Using Asynchronous Programming.
The name of a remote device can be queried for by taking the same
steps as for an address query, but setting the action flag of a
TInquirySockAddr
to KHostResName
. The name is
returned in the iName
member accessed through the
TNameEntry
.
// Now do name inquiry
addr.SetAction(KHostResName);
hr.GetByAddress(addr, entry, stat);
User::WaitForRequest(stat);
TPtrC deviceName;
if (stat == KErrNone)
deviceName.Set(entry().iName);
To do a simultaneous address and name inquiry, use
SetAction(KHostResName|KHostResInquiry)
.
RHostResolver::GetByName()
is not supported
This tutorial set takes you through all the steps involved in setting up and communicating over a Bluetooth connection.
Inquiring About Remote Devices - This document