Bluetooth discovery in Qt Mobility may not report devices (Nokia C6)

Bluetooth discovery in Qt Mobility does not report devices in the cache.

Article Metadata

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Code Example

Source file: http://doc.qt.nokia.com/qtmobility-1.2/btscanner.html

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Tested with

SDK: Nokia Qt SDK 1.1.4

Devices(s): Nokia C6-01

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Compatibility

Platform(s): Qt mobility 1.2.1 and later

Device(s): All with internal Bluetooth

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Platform Security

Signing Required: DevCert required

Capabilities: ReadDeviceData LocalServices WriteDeviceData

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Article

Keywords: QBluetoothDeviceDiscoveryAgent, BluetoothLinkManagerDeviceDiscoverer

Created: Devnull (24 Nov 2011)

Last edited: hamishwillee (29 Nov 2011)

Description

Qt Bluetooth device discovery is achieved using the Qt Mobility API QBluetoothDeviceDiscoveryAgent start() method. On Symbian this will only discover new devices, ignoring those that have been previously cached.

The reason for this is that the Symbian implementation explicitly ignores cached results by setting the KHostResIgnoreCache flag:

void BluetoothLinkManagerDeviceDiscoverer::startDiscovery(const uint discoveryType)
{
...
m_addr.SetAction(KHostResInquiry | KHostResName | KHostResIgnoreCache);
...	
}

How to reproduce

Pair with all local devices. Then attempt to discover the devices again. No devices are discovered - and in the Qt Creator debug window you can see the following messages

[Qt Message] void QtMobility::BluetoothLinkManagerDeviceDiscoverer::RunL() 0 
[Qt Message] void QtMobility::BluetoothLinkManagerDeviceDiscoverer::RunL() -25

Where -25 means KErrHostResNoMoreResults.

Solution

There is no known solution or workaround for the problem.