Question: allowing connection take-over

[stg]

Problem Description

Is is possible to allow a new connections (BluetoothA2DPSink) to take over even though a connection is currently esatblished?

The (real-world) issue I am having is that there are multiple users to a speaker, previous users device is still in range when another user wants to access the speaker. The speaker is an outdoor ceiling mounted device and thus not placed in a location where a "disconnect/pair" button is easily accessible.

This could certainly lead to multiple devices racing for access, but such bad implementations have become rare and are easily solved by set_address_validator and timer logic.

Device Description

ESP32

Sketch

Code not relevant for the issue

Other Steps to Reproduce

No response

Provide your Version of the EP32 Arduino Core (or the IDF Version)

3.0.1

I have checked existing issues, discussions and online documentation (incl. the Wiki)

• I confirm I have checked existing issues, discussions and online documentation (incl. the Wiki)

[pschatzmann]

I don't understand why you report this as a bug? So I converted it to a discussion:

If I remember right, when a user is connected, the system automatically set it to not connectable and discoverable.

I suggest that you try to set it to connectable and discoverable e.g. after some time after a user has connected.

[stg]

My apologies, posting in the wrong section was simply a mistake on my end.
Discussions are still relatively new (2020), and I do not use GitHub frequently.

I have tried:

• a2dp_sink.set_connectable(true);
• a2dp_sink.set_discoverability(ESP_BT_GENERAL_DISCOVERABLE);

Each on its own, and both together, a few seconds (up to a minute) after a connection is established.
Indeed, the A2DP sink becomes discoverable, and it is now possible to pair it with a new device, even when an existing connection is present.

However, it is still not possible to connect to the device.

These two lines are logged during such a failed connection attempt:

• [BluetoothA2DPSink.cpp] app_gap_callback(): [BT_AV] event: 16 when a connection attempt is started
• [BluetoothA2DPSink.cpp] app_gap_callback(): [BT_AV] event: 17 when a connection attempt is given up

They correspond to ESP_BT_GAP_ACL_CONN_CMPL_STAT_EVT and ESP_BT_GAP_ACL_DISCONN_CMPL_STAT_EVT.

At least on the ACL level, a connection is now allowed.
This does not happen unless calls to set_connectable and/or set_discoverable are made before attempting a new connection.

As an ugly hack I added case ESP_BT_GAP_ACL_CONN_CMPL_STAT_EVT: { disconnect(); } break; to BluetoothA2DPSink::app_gap_callback. This is obviously not the way. It does work to some extent - my phone neatly takes over the connection, but my computer does not (half-connected limbo state) and requires another disconnect/connect before success.

I fully understand that this is not necessarily related to ESP32-A2DP, but the underlying API and drivers.
Still, any suggestions are most warmly welcome.

[pschatzmann]

I do not recommend to change the source code directly. I recommend that you create a subclass and overwrite the method where you need some additional functionality as described here.