Detect desktop disconnects on Android

android/app/src/main/kotlin/com/wirelesstextsyncer/wireless_text_syncer_android/ConnectionService.kt

@@ -18,10 +18,13 @@ import okhttp3.Response
 import okhttp3.WebSocket
 import okhttp3.WebSocketListener
 import org.json.JSONObject
+import java.util.concurrent.TimeUnit
 
 class ConnectionService : Service() {
     private val tag = "WTS"
-    private val client = OkHttpClient()
+    private val client = OkHttpClient.Builder()
+        .pingInterval(5, TimeUnit.SECONDS)
+        .build()
 
     override fun onBind(intent: Intent?): IBinder? = null
 
@@ -103,6 +106,7 @@ class ConnectionService : Service() {
                     Log.d(tag, "Ignoring stale WebSocket onClosed")
                     return
                 }
+                currentSocket = null
                 updateState(connected = false, connecting = false, host = host, port = port, lastError = null)
                 Handler(Looper.getMainLooper()).post {
                     stopForeground(STOP_FOREGROUND_REMOVE)
@@ -115,12 +119,18 @@ class ConnectionService : Service() {
                     Log.d(tag, "Ignoring stale WebSocket onFailure")
                     return
                 }
+                currentSocket = null
+                val errorMessage = if (state.connected) {
+                    "桌面端服务已断开"
+                } else {
+                    t.message ?: "连接失败"
+                }
                 updateState(
                     connected = false,
                     connecting = false,
                     host = host,
                     port = port,
-                    lastError = t.message ?: "连接失败"
+                    lastError = errorMessage
                 )
                 Handler(Looper.getMainLooper()).post {
                     stopForeground(STOP_FOREGROUND_REMOVE)
@@ -243,7 +253,17 @@ class ConnectionService : Service() {
                     }
                 }
                 .toString()
-            return socket.send(payload)
+            val sent = socket.send(payload)
+            if (!sent && currentSocket == socket) {
+                currentSocket = null
+                updateState(
+                    connected = false,
+                    connecting = false,
+                    lastError = "连接已断开"
+                )
+            }
+
+            return sent
         }
 
         fun stateMap(): Map<String, Any?> {