Untested: WS battery improvement, relates to #113 and binwiederhier/ntfy#1662

app/src/main/java/io/heckel/ntfy/app/Application.kt

@@ -10,6 +10,7 @@ import io.heckel.ntfy.util.Log
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.launch
 
 class Application : Application() {
     val ioScope = CoroutineScope(SupervisorJob() + Dispatchers.IO)
@@ -34,7 +35,18 @@ class Application : Application() {
         val connectivityManager = getSystemService(CONNECTIVITY_SERVICE) as ConnectivityManager
         connectivityManager.registerDefaultNetworkCallback(object : ConnectivityManager.NetworkCallback() {
             override fun onAvailable(network: Network) {
-                SubscriberServiceManager.refresh(this@Application)
+                // Force reconnect of all WebSocket/JSON connections so they're rebound to the new
+                // default network. This catches Wi-Fi <-> cellular handoffs and similar transitions
+                // where the underlying socket is bound to a network that's no longer the default.
+                // Without this, broken connections would only be detected via the (potentially
+                // long) ping/pong timeout.
+                ioScope.launch {
+                    repository.getSubscriptions()
+                        .map { it.baseUrl }
+                        .distinct()
+                        .forEach { repository.incrementConnectionForceReconnectVersion(it) }
+                    SubscriberServiceManager.refresh(this@Application)
+                }
             }
             override fun onLost(network: Network) {
                 SubscriberServiceManager.refresh(this@Application)

app/src/main/java/io/heckel/ntfy/util/HttpUtil.kt

@@ -46,12 +46,24 @@ object HttpUtil {
 
     /**
      * Client for WebSocket connections.
-     * No read timeout, 1 minute ping interval, 10s connect timeout.
+     * No read timeout, 5 minute ping interval, 10s connect timeout.
+     *
+     * Dead connections are normally caught by one of two faster mechanisms:
+     *   1. Device-side network changes (Wi-Fi <-> cellular, network drop/return) are
+     *      detected instantly by Application.registerNetworkCallback's onAvailable
+     *      handler, which bumps connectionForceReconnectVersion to force a reconnect.
+     *   2. Server-side failures (crash, restart, server's own pong timeout) surface as
+     *      TCP FIN/RST and are detected instantly via OkHttp's onClosed/onFailure.
+     *
+     * The 5-minute client ping is only a fallback for the rare case where neither of
+     * the above fires: silent server hangs, NAT eviction, asymmetric routing breaks, etc.
+     * We use a long interval so the modem can fully power down between pings, which is
+     * the dominant battery factor for the foreground service.
      */
     suspend fun wsClient(context: Context, baseUrl: String): OkHttpClient {
         return emptyClientBuilder(context, baseUrl)
             .readTimeout(0, TimeUnit.MILLISECONDS)
-            .pingInterval(1, TimeUnit.MINUTES) // Technically not necessary, the server also pings us
+            .pingInterval(5, TimeUnit.MINUTES)
             .connectTimeout(10, TimeUnit.SECONDS)
             .build()
     }