No audio through the bluetooth headset - bluetooth

When i am connecting my phone to any handsfree device , the Voice is
not coming to the hands free device, when call is accepted using
handset/hands free.
The headset was paired and connected to the handset. Then accepted a
call. The voise was not coming in headset.
When i extracted the airlog i could find that the downlink( headset to
handset) is working fine.
But the uplink (phone to headset) is not sending the data over the sco
link.
Please anyone tell me the reason of this. When i checked the logs i
could see that the sco connection establishment was all proper.

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What's the difference between Jackdaw and KillerBee on RZ Raven USB Stick

What is the difference between Jackdaw and KillerBee on ZigBee USB Stick, both seem to be sniffing packet, but Jackdaw can act as a network interface, and KillerBee is only used for pentest? As far as I understand it, you can't use either to connect to like a hub or Wireless router, but only to ZigBee based devices, which would be the IoT devices such as sensors or smart socket etc.
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BlueZ which layer get reason of Bluetooth disconnection

I am using BlueZ stack for Bluetooth connection between Smart-phone(AG-Audio Gateway) and Embedded board(HF-Handsfree).
On which layer of Bluez ( HCI, L2CAP, RFCOMM) we will get reason of Bluetooth disconnection. So we can differentiate following type of disconnection:
Smart-Phone SIMPLE DISCONNECT, but phone is still have HF Embedded device in its paired list.
Smart-Phone FORGET HF device during bluetooth connection.
Disconnection because HF device went out of Smart-Phone bluetooth Range
HCI: Disconnection Complete Event, check the Reason byte.

How to switch wifi channel without dropping connection?

We are developing small internet connected device that connects via wifi and does some work. It is controlled via mobile app.
For configuration purposes we use wi-fi module that can work in both STA + AP modes simultaneously via two interfaces wlan0 and wlan1. One of the interfaces works in Master mode. Phone connects to the device via wlan1 and sends command for the device to connect to another network and waits for result. Device in turn connects to another wi-fi network using wlan0 and notifies the phone if connection was successful or not.
But there is one issue. Both interfaces (wlan0 and wlan1) must work on the same channel as we have single hardware module. This causes channel of wlan1 to change in order to match of channel for wlan0.
Here comes the problem. When channel changes phone looses connection with the device. Is there a way to change wi-fi channel but keep connection between the device and mobile phone?
Our wi-fi module is rtl8723bu.
Linux 3.4.103.
Wifi daemons: hostapd v0.8.x_rtw_r7475.20130812_beta, wpa_supplicant v2.3.
UPDATE
Here is more clearly description what is going on on device.
Let's assume that the phone already connected to Device wlan1 interface with essid DeviceAp which is on channel 1. We have a Router with essid RouterAp which is on channel 6. Device interface wlan0 is not configured and not running.
(Step1 on image below).
Then the phone sends a request to the device to connect to RouterAp.
(Step2 on image below).
When wlan0 starts connecting to RouterAp it changes working channel. Because WiFi module can work only on one channel. The channel of wlan1 also changes (maybe in hard way). Therefore Phone lost DeviceAp and starts roaming.
(Step3 on image below).
SO the update question is:
Is there a way to tell the Phone (or other device) about network change? Or perhaps increase the likelihood that the phone is connected back to DeviceAP.
This behavior is very similar to the process of setting up Google Chromecast.
Chromecast also has two wireless interfaces and change the channel, but the Phone does not lose connection with it.
Image:
http://postimg.org/image/soh78vd17/

To communicate between two bluetooth devices is pairing between them is necessary?

In general, two communicate between bluetooth devices, first we perform a bluetooth pairing between two devices and then starts further communication between them.
My problem scenario is simply to transfer a hello packet from one bluetooth device to another bluetooth device.
For this i am planning to use sockets programming technique i.e. RFCOMM sockets.
I got some help about this from http://people.csail.mit.edu/albert/bluez-intro/x502.html
So, my query is do we require bluetooth pairing between two devices before initiating communication with RFCOMM socket connection.
Or does 48 bits device address is only necessary to transfer some data packet from one bluetooth device to other and bluetooth pairing could be avoided.
No, it is not.
Bluetooth device can be in one of the four modes:
Broadcaster
Observer
Peripheral
Central
In broadcaster mode device can only send advertisement messages. This includes name and HwID.
In Observer mode device can only receive advertisement messages.
Peripheral = Broadcaster + can take in connect requests
Central = Observer + can send out connect requests.
If you have an application which does not want to connect use first two modes above.
Please let me know if this addresses your question.

HID Connection to a remote device without SDP record

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