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<concept xml:lang="en" id="GUID-CED041C8-D68D-55D1-957E-1A48EEFFF851"><title>Inquiring about Remote Devices</title><prolog><metadata><keywords/></metadata></prolog><conbody><p>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. </p> <section><title>How to inquire about remote devices</title> <p>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. </p> <p>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. </p> <p>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. </p> <p>Address and name inquiries are performed through the generic Symbian OS sockets class <xref href="GUID-B16CAD6D-85B1-3482-AAC0-9BADEDB6ABDD.dita"><apiname>RHostResolver</apiname></xref>. A specialist Bluetooth sockets address class, <xref href="GUID-0ECE42E1-5E04-3BFB-BA17-F8036510798D.dita"><apiname>TInquirySockAddr</apiname></xref>, which encapsulates Bluetooth address, Inquiry Access Code, and service and device classes, is provided for use with such inquiries. </p> <p><b> Basic Procedure</b> </p> <p>To inquire for the addresses of remote devices, take the following steps: </p> <ol id="GUID-B794CB43-DF26-5C9E-BABC-95E614B8225F"><li id="GUID-20EDA9A2-9C57-55E2-B36D-117CFF923D49"><p>Connect to the Sockets Server (<xref href="GUID-EF29C1D7-B1E5-370F-AE37-66231A6BE449.dita"><apiname>RSocketServ</apiname></xref>), and then select the protocol to be used using <xref href="GUID-EF29C1D7-B1E5-370F-AE37-66231A6BE449.dita#GUID-EF29C1D7-B1E5-370F-AE37-66231A6BE449/GUID-95B5BAA3-5A01-37F3-9C81-C5E71530B3B7"><apiname>RSocketServ::FindProtocol()</apiname></xref>. Address and name queries are supplied by the stack's BTLinkManager protocol layer, so select this. </p> </li> <li id="GUID-30F19EEC-CB83-53D4-99E6-84C68A2DED9C"><p>Create and initialise an <xref href="GUID-B16CAD6D-85B1-3482-AAC0-9BADEDB6ABDD.dita"><apiname>RHostResolver</apiname></xref> object. </p> </li> <li id="GUID-B2FD4AE2-A5DE-5EB4-A135-CDA502364550"><p>Set the <codeph>TInquirySockAddr</codeph> parameter for the inquiry: for address inquiries, the <xref href="GUID-75438E00-D211-3C94-A47D-61C5644A667D.dita"><apiname>KHostResInquiry</apiname></xref> flag must be set through <xref href="GUID-0ECE42E1-5E04-3BFB-BA17-F8036510798D.dita#GUID-0ECE42E1-5E04-3BFB-BA17-F8036510798D/GUID-E4E83FA5-3102-3CE8-8796-A70C017D4FC7"><apiname>TInquirySockAddr::SetAction()</apiname></xref>. </p> <p>The query can then be started with <xref href="GUID-B16CAD6D-85B1-3482-AAC0-9BADEDB6ABDD.dita#GUID-B16CAD6D-85B1-3482-AAC0-9BADEDB6ABDD/GUID-B210BAF2-1D26-3F5A-8EBE-EF5B460A69E1"><apiname>RHostResolver::GetByAddress()</apiname></xref>. </p> </li> <li id="GUID-85980345-3E1A-5E10-A9F0-547DECBE52BB"><p>When <codeph>GetByAddress()</codeph> completes, it fills in a <xref href="GUID-C625E339-6726-3FB9-8F8A-F4DB0CAC15FF.dita"><apiname>TNameEntry</apiname></xref> object with the address and class of the first device found (or is undefined if no device was found). </p> </li> <li id="GUID-B2FE92B6-989A-5A9F-92CB-9759587C31F8"><p>To get all the devices discovered, call <xref href="GUID-B16CAD6D-85B1-3482-AAC0-9BADEDB6ABDD.dita#GUID-B16CAD6D-85B1-3482-AAC0-9BADEDB6ABDD/GUID-B64AB6BA-6D1D-30EB-88EF-381B52939F3D"><apiname>RHostResolver::Next()</apiname></xref> repeatedly until <codeph>KErrHostResNoMoreResults</codeph> is returned. </p> </li> </ol> <p><b>Getting the addresses of remote devices</b> </p> <p>The following example shows how to start a remote device address inquiry. </p> <ol id="GUID-A31D5876-7EE5-56B6-8F5A-7B8986C55349"><li id="GUID-B6BCA711-BBC7-52C0-9B7A-F128031346ED"><p>Connect to the socket server </p> <codeblock id="GUID-9E81DC37-FFC5-5427-BC01-54DFD82ED929" xml:space="preserve">RSocketServ socketServ;

socketServ.Connect();

TProtocolDesc pInfo;

_LIT(KL2Cap, "BTLinkManager");

User::LeaveIfError(socketServ.FindProtocol(KL2Cap,pInfo));</codeblock> </li> <li id="GUID-48A0FDB1-BB15-5759-8AC1-F837513B423A"><p>Create and initialise an <codeph>RHostResolver</codeph>  </p> <codeblock id="GUID-221037A8-6A39-5C27-A0DD-2A2BD14E5A7F" xml:space="preserve">RHostResolver hr;

User::LeaveIfError(hr.Open(socketServ,pInfo.iAddrFamily,pInfo.iProtocol));</codeblock> </li> <li id="GUID-4A5D7DFC-FDFE-5D87-8DAB-A1BE59EFF806"><p>Set up a discovery query and start it </p> <codeblock id="GUID-DA8F9430-CDE6-5663-9DED-D897B134DEEF" xml:space="preserve">TInquirySockAddr addr;

TNameEntry entry;

addr.SetIAC(KGIAC);

addr.SetAction(KHostResInquiry);

TRequestStatus status;

hr.GetByAddress(addr, entry, status);

User::WaitForRequest(status);</codeblock> </li> <li id="GUID-9835B54E-E6D2-5FD5-8E7C-1374177F2D8A"><p>Process the information returned in <codeph>entry</codeph>  </p> <codeblock id="GUID-766A738A-2F2F-5570-964B-196FA45BA601" xml:space="preserve">...</codeblock> </li> </ol> <p><b>Notes:</b> </p> <ul><li id="GUID-71BF7F7E-AD6E-5715-B9A5-BAE7488B9B80"><p> <xref href="GUID-0ECE42E1-5E04-3BFB-BA17-F8036510798D.dita#GUID-0ECE42E1-5E04-3BFB-BA17-F8036510798D/GUID-B8F50B34-789B-3ADE-8D1E-04B59394BC2A"><apiname>TInquirySockAddr::SetIAC()</apiname></xref> sets the Bluetooth Inquiry Access Code. For more information, see <xref scope="external" href="http://www.bluetooth.org/assigned-numbers/">Bluetooth Assigned Numbers</xref>. </p> </li> <li id="GUID-B55A03AB-3F37-5377-80E6-5F94045A4C5F"><p>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. </p> </li> <li id="GUID-51CA2D0D-6A75-537F-A040-EA47D00DFEE0"><p>Communications API calls are typically asynchronous (indicated by a <xref href="GUID-E0B34F3E-D4C4-3232-B8B1-7DB35B454646.dita"><apiname>TRequestStatus</apiname></xref> parameter in the call). It is recommended that such calls are encapsulated in active objects, as explained in <xref href="GUID-B507490F-6BD3-5DF5-97E4-EFDFEA2B4EDD.dita">Using Asynchronous Programming</xref>. </p> </li> </ul> <p><b>Getting the name of a remote device</b> </p> <p>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 <codeph>TInquirySockAddr</codeph> to <xref href="GUID-8B748089-6177-3C64-8F54-C2F6E1C364F4.dita"><apiname>KHostResName</apiname></xref>. The name is returned in the <codeph>iName</codeph> member accessed through the <codeph>TNameEntry</codeph>. </p> <p><b>Example </b> </p> <codeblock id="GUID-F670B724-E96C-5077-9317-4A6F27CBFF67" xml:space="preserve">// Now do name inquiry

addr.SetAction(KHostResName);

hr.GetByAddress(addr, entry, stat);

User::WaitForRequest(stat);

TPtrC deviceName;

if (stat == KErrNone)