Add L2CAP channel support - #1231
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Adds `L2CapSocket`, a connection-oriented channel opened from a connected peripheral: `AndroidPeripheral.openL2CapChannel` / `openInsecureL2CapChannel` and `CoreBluetoothPeripheral.openL2CapChannel`. The socket is a bidirectional byte stream (`read` into a buffer, `write` a packet, `close`) exposing `isConnected` / `hasReachedEof` state; failures surface as `L2CapException`. Android wraps `BluetoothDevice.createL2capChannel`, connecting on `Dispatchers.IO`. Apple confines the `CBL2CAPChannel` NSStreams to a single dedicated run-loop thread (they are not safe to drive from a rotating dispatcher pool) and serializes opens through the connection's guard, since CoreBluetooth's `didOpenL2CAPChannel` callback carries no PSM and so cannot be correlated to a request; a channel delivered to a cancelled or disconnected open is torn down rather than leaked. Closing (or abandoning) a socket must actually free the PSM: CoreBluetooth only disconnects a channel when the CBL2CAPChannel deallocates — closing its streams is not enough — and Kotlin/Native releases Obj-C references at collection time, so teardown drops the channel reference and close() forces a collection. Without that, reopening the same PSM fails with "L2CAP PSM already connected" until an incidental GC runs.
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Reviewed by Cursor Bugbot for commit 58ed1f4. Configure here.
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Adapted from #1023, and completing the implementation for both iOS and Android. Tested on both platforms with real devices, and also from macOS to iOS.
Adds
L2CapSocket, a connection-oriented channel opened from a connected peripheral:AndroidPeripheral.openL2CapChannel/openInsecureL2CapChannelandCoreBluetoothPeripheral.openL2CapChannel. The socket is a bidirectional byte stream (readinto a buffer,writea packet,close) exposingisConnected/hasReachedEofstate; failures surface asL2CapException.Android wraps
BluetoothDevice.createL2capChannel, connecting onDispatchers.IO. Apple confines theCBL2CAPChannelNSStreams to a single dedicated run-loop thread (they are not safe to drive from a rotating dispatcher pool) and serializes opens through the connection's guard, since CoreBluetooth'sdidOpenL2CAPChannelcallback carries no PSM and so cannot be correlated to a request; a channel delivered to a cancelled or disconnected open is torn down rather than leaked.Closes #810 #588 #1023.
Note
Medium Risk
New BLE transport path with substantial Apple concurrency/GC lifecycle logic; failures are mostly additive but incorrect teardown could leave PSMs stuck or leak channels until GC.
Overview
Adds L2CAP CoC alongside GATT: a new
L2CapSocketbyte-stream API andL2CapException, opened from connected platform peripherals after a GATT link exists.On Android (API 29+),
AndroidPeripheralexposes secure and insecure opens viaBluetoothDeviceL2CAP sockets, with I/O onDispatchers.IOand socket cleanup on failed/cancelled connect.On Apple,
CoreBluetoothPeripheral.openL2CapChanneldrivesCBPeripheral.openL2CAPChannel; opens are single-flight under the connection guard becausedidOpenL2CAPChannelhas no PSM.AppleL2CapSocketruns allNSStreamwork on a dedicated run-loop thread, retains/releasesCBL2CAPChannelfor lifecycle (includingGC.collect()onclose()), and abandons channels delivered after cancel/disconnect to avoid leaks or “PSM already connected”.README documents usage; JVM API surface is updated in
kable-core.api.Reviewed by Cursor Bugbot for commit 58ed1f4. Configure here.