Auto-Connect/Re-connect Issue with Ble Manager in React Native

[prabu-nesh]

I'm facing an issue with auto-connecting and re-connecting devices using BleManager in React Native. The connection process is working for the initial connection, but the subsequent reconnect attempts are failing. The goal is to connect to a peripheral, set the MTU size, retrieve services, and handle the connected device's characteristics. However, the reconnect logic does not seem to be functioning as expected.

Here is the code that I am currently using:

const onConnect = async (item) => {
try {
await new Promise(async () => {
await BleManager.connect(item);
// Await the MTU request
await BleManager.requestMTU(item, 517);
BleManager.retrieveServices(item).then((res) => {
// handle characteristics response
});
});
} catch (error) {
console.error("Connection error:", error);
}
};

const onConnectedDevices = async () => {
await BleManager.getConnectedPeripherals([]).then(async (peripherals) => {
if (peripherals.length > 0) {
onConnect(peripherals[0]?.id);
}
});
};

Expected Behavior:

• The first connection attempt should succeed, and the MTU request and service retrieval should work fine.
• On subsequent calls to onConnectedDevices, the device should reconnect successfully and handle the same operations (MTU request, retrieve services).

Current Behavior:

• The initial connection works as expected, but the reconnection does not establish a stable connection.
• The device may appear as connected, but operations like MTU size adjustment and service retrieval fail.
• No error message is thrown, making it difficult to debug.

[rakshitbharat]

same here

[Aharta]

Hey @prabu-nesh @rakshitbharat , Thanks for sharing the problem, Here is my take into this -

• First Issue that I found is in the await BleManager.requestMTU(item, 517) function, first parameter is peripheral's ID and second is the MTU size, where we can set the maximum value of 512, but you have set it to 517 which exceeds the limit. Try to set the value to 512.
• Second is the method that you are using BleManager.getConnectedPeripherals([]), I think you have to pass serviceUUIDs to this Array, can take a look into this.

Here is the solution you can try (as I was also facing the same Issue, and I resolved it by doing this):
Whenever you initialize the BleManager.start() method, add restoreIdentifierKey: "test" and forceLegacy: true, This is the example for that :-
BleManager.start({
showAlert: false,
restoreIdentifierKey: "test",
forceLegacy: true,
})
By doing this what will happen is
restoreIdentifierKey(ios) : Enables background restoration of BLE state after app termination/restart.
forceLegacy : This option forces the library to use legacy scanning APIs on Android.

Let me know the further Updates regarding this, Thank You and Happy Hacking !