fix: detect and close connections on physical device disconnect

android/src/main/kotlin/com/flutter_classic_bluetooth/flutter_classic_bluetooth/FlutterClassicBluetoothPlugin.kt

@@ -6,6 +6,7 @@ import android.bluetooth.BluetoothDevice
 import android.bluetooth.BluetoothManager
 import android.content.Context
 import android.content.Intent
+import android.content.IntentFilter
 import android.content.pm.PackageManager
 import android.os.Build
 import android.os.Handler
@@ -48,6 +49,11 @@ class FlutterClassicBluetoothPlugin :
     // (platform) thread; Bluetooth I/O runs on background threads.
     private val mainHandler = Handler(Looper.getMainLooper())
 
+    // Detects when a remote Bluetooth device physically disconnects (e.g.
+    // printer turned off) and emits "disconnected" on the matching connection's
+    // state stream.
+    private var aclDisconnectReceiver: AclDisconnectReceiver? = null
+
     // Event channels
     private lateinit var adapterStateChannel: EventChannel
     private lateinit var discoveryStateChannel: EventChannel
@@ -75,10 +81,17 @@ class FlutterClassicBluetoothPlugin :
 
         bondStateChannel = EventChannel(messenger, BluetoothHelper.BOND_STATE_CHANNEL)
         bondStateChannel.setStreamHandler(BondStateReceiver(context))
+
+        aclDisconnectReceiver = AclDisconnectReceiver(connections)
+        BluetoothHelper.registerExportedReceiver(
+            context, aclDisconnectReceiver!!, IntentFilter(BluetoothDevice.ACTION_ACL_DISCONNECTED)
+        )
     }
 
     override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
         channel.setMethodCallHandler(null)
+        aclDisconnectReceiver?.let { context.unregisterReceiver(it) }
+        aclDisconnectReceiver = null
         closeAll()
     }
 

android/src/main/kotlin/com/flutter_classic_bluetooth/flutter_classic_bluetooth/receivers/AclDisconnectReceiver.kt

@@ -0,0 +1,42 @@
+package com.flutter_classic_bluetooth.flutter_classic_bluetooth.receivers
+
+import android.bluetooth.BluetoothDevice
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.os.Build
+import android.util.SparseArray
+import com.flutter_classic_bluetooth.flutter_classic_bluetooth.BluetoothConnectionWrapper
+
+// Listens for system ACL disconnection events so we can immediately close the
+// matching connection when a remote device goes away (e.g. printer turned off
+// or moves out of range). The wrapper's close() emits "disconnected" on its
+// state stream, so Dart is notified without extra plumbing here.
+class AclDisconnectReceiver(
+    private val connections: SparseArray<BluetoothConnectionWrapper>
+) : BroadcastReceiver() {
+
+    @Suppress("MissingPermission")
+    override fun onReceive(ctx: Context, intent: Intent) {
+        if (intent.action != BluetoothDevice.ACTION_ACL_DISCONNECTED) return
+
+        val device = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+            intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE, BluetoothDevice::class.java)
+        } else {
+            @Suppress("DEPRECATION")
+            intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE)
+        } ?: return
+
+        val address = device.address
+        synchronized(connections) {
+            for (i in 0 until connections.size()) {
+                val conn = connections.valueAt(i)
+                if (conn.address == address) {
+                    conn.close()
+                    connections.removeAt(i)
+                    break
+                }
+            }
+        }
+    }
+}

ios/flutter_classic_bluetooth/Sources/flutter_classic_bluetooth/FlutterClassicBluetoothPlugin.swift

@@ -25,6 +25,28 @@ public class FlutterClassicBluetoothPlugin: NSObject, FlutterPlugin {
         adapterChannel.setStreamHandler(instance.adapterStateHandler)
 
         registrar.addMethodCallDelegate(instance, channel: channel)
+
+        EAAccessoryManager.shared().registerForLocalNotifications()
+        NotificationCenter.default.addObserver(
+            instance,
+            selector: #selector(accessoryDidDisconnect(_:)),
+            name: .EAAccessoryDidDisconnect,
+            object: nil
+        )
+    }
+
+    @objc private func accessoryDidDisconnect(_ notification: Notification) {
+        guard let accessory = notification.userInfo?[EAAccessoryKey] as? EAAccessory else {
+            return
+        }
+        for (id, wrapper) in connections {
+            if wrapper.accessoryConnectionID == accessory.connectionID {
+                wrapper.close()
+                connections.removeValue(forKey: id)
+
+                break
+            }
+        }
     }
 
     public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) {
@@ -195,7 +217,7 @@ public class FlutterClassicBluetoothPlugin: NSObject, FlutterPlugin {
         let connId = nextConnectionId
         nextConnectionId += 1
 
-        let wrapper = EASessionWrapper(id: connId, session: session, messenger: messenger)
+        let wrapper = EASessionWrapper(id: connId, session: session, accessoryConnectionID: accessory.connectionID, messenger: messenger)
         wrapper.startReading()
         connections[connId] = wrapper
 
@@ -249,13 +271,15 @@ public class FlutterClassicBluetoothPlugin: NSObject, FlutterPlugin {
 
 class EASessionWrapper: NSObject, StreamDelegate {
     let id: Int
+    let accessoryConnectionID: Int
     private let session: EASession
     private var messenger: FlutterBinaryMessenger
     private var dataStreamHandler: IOSStreamHandler?
     private var stateStreamHandler: IOSStreamHandler?
 
-    init(id: Int, session: EASession, messenger: FlutterBinaryMessenger) {
+    init(id: Int, session: EASession, accessoryConnectionID: Int, messenger: FlutterBinaryMessenger) {
         self.id = id
+        self.accessoryConnectionID = accessoryConnectionID
         self.session = session
         self.messenger = messenger
         super.init()