BLE client hangs when conn_id/m_appId reaches 255

[xdxita]

Hi everyone!

Here's my scenario, I've a ESP32 (ESP32-DevKit board) that connects to a server (always the same), fetch some data and disconnect from it, the connection and disconnection is initiated by my code. This connect/disconnect loop is done several times during the day because the server isn't always close.

After some time I've noticed that the code hanged at bleClient->connect(advDevice);, enabling CORE_DEBUG_LEVEL to show INFO logs I've found out that the code hangs when m_appId reaches 255 because the last log output is:
[BLEDevice.cpp:623] addPeerDevice(): add conn_id: 1, GATT role: client
Looks like m_appId/conn_id increments every time a connection is made and it never decrementes.
I've changed CORE_DEBUG_LEVEL to VERBOSE to get more details:

[2096656][V][BLEClient.cpp:98] connect(): >> connect(ea:10:d6:ed:8d:68)
[2096662][I][BLEDevice.cpp:623] addPeerDevice(): add conn_id: 255, GATT role: client
[2096670][V][FreeRTOS.cpp:189] take(): Semaphore taking: name: RegEvt (0x3ffe9e60), owner: <N/A> for connect
[2096680][V][FreeRTOS.cpp:198] take(): Semaphore taken: name: RegEvt (0x3ffe9e60), owner: connect
[2096689][V][FreeRTOS.cpp:63] wait(): >> wait: Semaphore waiting: name: RegEvt (0x3ffe9e60), owner: connect for connect
[2096689][D][BLEDevice.cpp:148] gattClientEventHandler(): gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_REG_EVT
[2096710][V][BLEUtils.cpp:1283] dumpGattClientEvent(): GATT Event: ESP_GATTC_REG_EVT
[2096718][V][BLEUtils.cpp:1444] dumpGattClientEvent(): [status: ESP_GATT_OK, app_id: 0xff]
[2096726][D][BLEClient.cpp:178] gattClientEventHandler(): gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_REG_EVT
[2096737][V][FreeRTOS.cpp:143] give(): Semaphore giving: name: RegEvt (0x3ffe9e60), owner: connect
[2096746][V][FreeRTOS.cpp:77] wait(): << wait: Semaphore released: name: RegEvt (0x3ffe9e60), owner: <N/A>
[2096756][V][FreeRTOS.cpp:189] take(): Semaphore taking: name: OpenEvt (0x3ffe9304), owner: <N/A> for connect
[2096765][V][FreeRTOS.cpp:198] take(): Semaphore taken: name: OpenEvt (0x3ffe9304), owner: connect
[2096775][V][FreeRTOS.cpp:63] wait(): >> wait: Semaphore waiting: name: OpenEvt (0x3ffe9304), owner: connect for connect
[2098640][D][BLEDevice.cpp:148] gattClientEventHandler(): gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_CONNECT_EVT
[2098651][V][BLEUtils.cpp:1283] dumpGattClientEvent(): GATT Event: ESP_GATTC_CONNECT_EVT
[2098660][V][BLEUtils.cpp:1311] dumpGattClientEvent(): [conn_id: 0, remote_bda: ea:10:d6:ed:8d:68]
[2098669][D][BLEClient.cpp:178] gattClientEventHandler(): gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_CONNECT_EVT
[2098680][D][BLEDevice.cpp:607] updatePeerDevice(): update conn_id: 255, GATT role: client
[2098689][D][BLEDevice.cpp:148] gattClientEventHandler(): gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_OPEN_EVT
[2098700][V][BLEUtils.cpp:1283] dumpGattClientEvent(): GATT Event: ESP_GATTC_OPEN_EVT
[2098708][V][BLEUtils.cpp:1402] dumpGattClientEvent(): [status: ESP_GATT_OK, conn_id: 0, remote_bda: ea:10:d6:ed:8d:68, mtu: 23]
[2099522][V][BLEUtils.cpp:951] gattClientEventTypeToString(): Unknown GATT Client event type: 46
[2099521][D][BLEDevice.cpp:148] gattClientEventHandler(): gattClientEventHandler [esp_gatt_if: 4] ... Unknown
[2099542][V][BLEUtils.cpp:951] gattClientEventTypeToString(): Unknown GATT Client event type: 46
[2099542][V][BLEUtils.cpp:1283] dumpGattClientEvent(): GATT Event: Unknown
[2099558][D][BLEDevice.cpp:148] gattClientEventHandler(): gattClientEventHandler [esp_gatt_if: 4] ... ESP_GATTC_CFG_MTU_EVT
[2099569][V][BLEUtils.cpp:1283] dumpGattClientEvent(): GATT Event: ESP_GATTC_CFG_MTU_EVT
[2103791][V][BLEUtils.cpp:1049] dumpGapEvent(): Received a GAP event: ESP_GAP_BLE_UPDATE_CONN_PARAMS_EVT
[2103801][V][BLEUtils.cpp:1253] dumpGapEvent(): [status: 0, bd_addr: ea:10:d6:ed:8d:68, min_int: 16, max_int: 60, latency: 0, conn_int: 60, timeout: 400]
[2103815][D][BLEClient.cpp:493] handleGAPEvent(): BLEClient ... handling GAP event!

Looks like the code is waiting for the OpenEvt semaphore that usually is given at ESP_GATTC_OPEN_EVT that never happens.

But why?

Additional information, once the code disconnects from the server with bleClient->disconnect() then I check for bleClient->isConnected() before BLEDevice::deinit() to free resources for other tasks.