Inquiring +about Remote Devices

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.

How to inquire about remote devices

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 platform 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.

Basic +Procedure

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.

Getting +the addresses of remote devices

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
...

Notes:

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.

Getting +the name of a remote device

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.

Example

// Now do name inquiry +addr.SetAction(KHostResName); +hr.GetByAddress(addr, entry, stat); +User::WaitForRequest(stat); +TPtrC deviceName; +if (stat == KErrNone) + deviceName.Set(entry().iName);

Notes

To do a simultaneous +address and name inquiry, use SetAction(KHostResName|KHostResInquiry).
RHostResolver::GetByName() is +not supported