Fix stale packager connections on Android

DevServerHelper opened and closed the packager connection in separate
AsyncTasks on THREAD_POOL_EXECUTOR. A close could run before a pending
open, and repeated opens could create two clients. Changing the bundle
location from the dev menu also kept the old connection. In both cases,
the old dev server could still reload the app.

- Run openPackagerConnection and closePackagerConnection as tasks on one
  single-threaded executor. Tasks run in call order, off the UI thread,
  and only that thread uses packagerClient. The executor names its
  thread ReactPackagerConnection and stops it after 30 seconds without
  work.
- Remember the host of the open client. If an open finds a client for a
  different host, close it and connect to the new host.
- Check clientId on the caller's thread. A failed init() still crashes
  the app, as before; packagerClient stays null, so a later open can
  retry.
- Change Bundle Location: close the packager connection before the
  reload, as setBundleSource does. Trim the input, then reject a host
  that OkHttp cannot parse in the connection URL and show a toast.
  Before, an invalid host was saved without a check.
- ReconnectingWebSocket: change close state under the socket's monitor,
  so no message handler starts after closeQuietly() returns. Close a
  socket whose handshake finishes after closeQuietly() instead of
  reporting it as connected.
- Add DevServerHelperTest, ReconnectingWebSocketTest and
  DevSupportHttpClientTest.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: vonovak

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/devsupport/DevServerHelper.kt

@@ -16,6 +16,7 @@ import android.content.Context
 import android.net.Uri
 import android.os.AsyncTask
 import android.provider.Settings.Secure
+import androidx.annotation.VisibleForTesting
 import com.facebook.common.logging.FLog
 import com.facebook.react.bridge.ReactContext
 import com.facebook.react.common.ReactConstants
@@ -39,6 +40,10 @@ import java.io.UnsupportedEncodingException
 import java.security.MessageDigest
 import java.security.NoSuchAlgorithmException
 import java.util.Locale
+import java.util.concurrent.Executor
+import java.util.concurrent.LinkedBlockingQueue
+import java.util.concurrent.ThreadPoolExecutor
+import java.util.concurrent.TimeUnit
 import okhttp3.Call
 import okhttp3.Callback
 import okhttp3.OkHttpClient
@@ -73,7 +78,8 @@ public open class DevServerHelper(
 
     public fun onPackagerDevMenuCommand()
 
-    // Allow apps to provide listeners for custom packager commands.
+    // Allow apps to provide listeners for custom packager commands. Handlers must not block,
+    // because closing the connection waits for a running handler.
     public fun customCommandHandlers(): Map<String, RequestHandler>?
   }
 
@@ -87,7 +93,14 @@ public open class DevServerHelper(
   private val packagerStatusCheck: PackagerStatusCheck = PackagerStatusCheck(client)
   private val packageName: String = applicationContext.packageName
 
+  // Must stay single-threaded: open and close have to run in call order.
+  @VisibleForTesting
+  internal var packagerConnectionExecutor: Executor =
+      ThreadPoolExecutor(0, 1, 30, TimeUnit.SECONDS, LinkedBlockingQueue()) { runnable ->
+        Thread(runnable, PACKAGER_CONNECTION_THREAD_NAME)
+      }
   private var packagerClient: JSPackagerClient? = null
+  private var packagerClientHost: String? = null
   private var inspectorPackagerConnection: IInspectorPackagerConnection? = null
 
   /** Returns an opaque ID which is stable for the current combination of device and app, stable */
@@ -138,65 +151,62 @@ public open class DevServerHelper(
     get() = settings.isJSMinifyEnabled
 
   public fun openPackagerConnection(clientId: String?, commandListener: PackagerCommandListener) {
-    if (packagerClient != null) {
-      FLog.w(ReactConstants.TAG, "Packager connection already open, nooping.")
-      return
-    }
-    object : AsyncTask<Void, Void, Void>() {
-          @Deprecated("This needs to be rewritten to not use AsyncTasks")
-          override fun doInBackground(vararg backgroundParams: Void): Void? {
-            val handlers: MutableMap<String, RequestHandler> = mutableMapOf()
-            handlers["reload"] =
-                object : NotificationOnlyHandler() {
-                  override fun onNotification(params: Any?) {
-                    commandListener.onPackagerReloadCommand()
-                  }
-                }
-            handlers["devMenu"] =
-                object : NotificationOnlyHandler() {
-                  override fun onNotification(params: Any?) {
-                    commandListener.onPackagerDevMenuCommand()
-                  }
-                }
-            commandListener.customCommandHandlers()?.let { handlers.putAll(it) }
-
-            val onPackagerConnectedCallback: ReconnectingWebSocket.ConnectionCallback =
-                object : ReconnectingWebSocket.ConnectionCallback {
-                  override fun onConnected() {
-                    commandListener.onPackagerConnected()
-                  }
-
-                  override fun onDisconnected() {
-                    commandListener.onPackagerDisconnected()
-                  }
-                }
-
-            checkNotNull(clientId)
-            packagerClient =
-                JSPackagerClient(
-                        clientId,
-                        packagerConnectionSettings,
-                        handlers,
-                        onPackagerConnectedCallback,
-                    )
-                    .apply { init() }
+    val id = checkNotNull(clientId)
+    packagerConnectionExecutor.execute {
+      val host = packagerConnectionSettings.debugServerHost
+      packagerClient?.let { client ->
+        if (host == packagerClientHost) {
+          FLog.w(ReactConstants.TAG, "Packager connection already open, nooping.")
+          return@execute
+        }
+        // The dev server host changed without a close.
+        client.close()
+        packagerClient = null
+      }
+      val handlers: MutableMap<String, RequestHandler> = mutableMapOf()
+      handlers["reload"] =
+          object : NotificationOnlyHandler() {
+            override fun onNotification(params: Any?) {
+              commandListener.onPackagerReloadCommand()
+            }
+          }
+      handlers["devMenu"] =
+          object : NotificationOnlyHandler() {
+            override fun onNotification(params: Any?) {
+              commandListener.onPackagerDevMenuCommand()
+            }
+          }
+      commandListener.customCommandHandlers()?.let { handlers.putAll(it) }
 
-            return null
+      val onPackagerConnectedCallback: ReconnectingWebSocket.ConnectionCallback =
+          object : ReconnectingWebSocket.ConnectionCallback {
+            override fun onConnected() {
+              commandListener.onPackagerConnected()
+            }
+
+            override fun onDisconnected() {
+              commandListener.onPackagerDisconnected()
+            }
           }
-        }
-        .executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR)
+
+      packagerClient =
+          JSPackagerClient(
+                  id,
+                  packagerConnectionSettings,
+                  handlers,
+                  onPackagerConnectedCallback,
+              )
+              .apply { init() }
+      packagerClientHost = host
+    }
   }
 
   public fun closePackagerConnection() {
-    object : AsyncTask<Void, Void, Void>() {
-          @Deprecated("This class needs to be rewritten to don't use AsyncTasks")
-          override fun doInBackground(vararg params: Void): Void? {
-            packagerClient?.close()
-            packagerClient = null
-            return null
-          }
-        }
-        .executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR)
+    packagerConnectionExecutor.execute {
+      packagerClient?.close()
+      packagerClient = null
+      packagerClientHost = null
+    }
   }
 
   public fun openInspectorConnection() {
@@ -385,6 +395,7 @@ public open class DevServerHelper(
 
   private companion object {
     private const val DEBUGGER_MSG_DISABLE = "{ \"id\":1,\"method\":\"Debugger.disable\" }"
+    private const val PACKAGER_CONNECTION_THREAD_NAME = "ReactPackagerConnection"
 
     private fun getSHA256(string: String): String {
       val digest =

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/devsupport/DevSupportManagerBase.kt

@@ -52,6 +52,7 @@ import com.facebook.react.devsupport.DevServerHelper.PackagerCommandListener
 import com.facebook.react.devsupport.InspectorFlags.getFuseboxEnabled
 import com.facebook.react.devsupport.StackTraceHelper.convertJavaStackTrace
 import com.facebook.react.devsupport.StackTraceHelper.convertJsStackTrace
+import com.facebook.react.devsupport.inspector.DevSupportHttpClient
 import com.facebook.react.devsupport.inspector.TracingState
 import com.facebook.react.devsupport.inspector.TracingStateProvider
 import com.facebook.react.devsupport.interfaces.BundleLoadCallback
@@ -450,9 +451,24 @@ public abstract class DevSupportManagerBase(
             return@DevOptionHandler
           }
 
-          ChangeBundleLocationDialog.show(context, devSettings) { host: String ->
-            devSettings.packagerConnectionSettings.debugServerHost = host
-            handleReloadJS()
+          ChangeBundleLocationDialog.show(context, devSettings) { input: String ->
+            val host = input.trim()
+            // An empty host resets to the default. An invalid host would crash the connection.
+            if (host.isEmpty() || DevSupportHttpClient.isValidHost(host)) {
+              devSettings.packagerConnectionSettings.debugServerHost = host
+              devServerHelper.closePackagerConnection()
+              handleReloadJS()
+            } else {
+              Toast.makeText(
+                      applicationContext,
+                      applicationContext.getString(
+                          R.string.catalyst_change_bundle_location_invalid,
+                          host,
+                      ),
+                      Toast.LENGTH_LONG,
+                  )
+                  .show()
+            }
           }
         }
 

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/devsupport/inspector/DevSupportHttpClient.kt

@@ -13,6 +13,7 @@ import com.facebook.react.modules.network.OkHttpClientProvider
 import java.util.concurrent.TimeUnit
 import okhttp3.ConnectionPool
 import okhttp3.Dispatcher
+import okhttp3.HttpUrl.Companion.toHttpUrlOrNull
 import okhttp3.OkHttpClient
 
 /**
@@ -68,4 +69,10 @@ internal object DevSupportHttpClient {
    * the host specifies port 443 explicitly (e.g. "example.com:443").
    */
   internal fun wsScheme(host: String): String = if (host.endsWith(":443")) "wss" else "ws"
+
+  /**
+   * Returns whether OkHttp can build a request for the given host, for example "localhost:8081".
+   */
+  internal fun isValidHost(host: String): Boolean =
+      "${httpScheme(host)}://$host/".toHttpUrlOrNull() != null
 }

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/packagerconnection/ReconnectingWebSocket.kt

@@ -77,16 +77,18 @@ public class ReconnectingWebSocket(
   }
 
   public fun closeQuietly() {
-    closed = true
-    closeWebSocketQuietly()
-    messageCallback = null
+    synchronized(this) {
+      closed = true
+      closeWebSocketQuietly()
+      messageCallback = null
+    }
 
     connectionCallback?.onDisconnected()
   }
 
   private fun closeWebSocketQuietly() {
     try {
-      webSocket?.close(1_000, "End of session")
+      webSocket?.close(CLOSE_NORMAL, CLOSE_REASON)
     } catch (e: Exception) {
       // swallow, no need to handle it here
     }
@@ -100,6 +102,10 @@ public class ReconnectingWebSocket(
 
   @Synchronized
   override fun onOpen(webSocket: WebSocket, response: Response) {
+    if (closed) {
+      webSocket.close(CLOSE_NORMAL, CLOSE_REASON)
+      return
+    }
     this.webSocket = webSocket
     suppressConnectionErrors = false
 
@@ -155,5 +161,7 @@ public class ReconnectingWebSocket(
     private val TAG: String = ReconnectingWebSocket::class.java.simpleName
 
     private const val RECONNECT_DELAY_MS = 2_000L
+    private const val CLOSE_NORMAL = 1_000
+    private const val CLOSE_REASON = "End of session"
   }
 }

packages/react-native/ReactAndroid/src/main/res/devsupport/values/strings.xml

@@ -8,6 +8,7 @@
   <string name="catalyst_change_bundle_location_instructions" project="catalyst" translatable="false">You can connect either via USB (localhost - default) or Wifi. If you connect via USB and running with a physical device, make sure you:\n 1. Connect your device via USB\n 2. Set the bundle location to `localhost:8081`\n 3. Run this command in your terminal:\n&#160;&#160;&#160;&#160;&#160;&#160;`%1$s`</string>
   <string name="catalyst_change_bundle_location_apply" project="catalyst" translatable="false">Apply Changes</string>
   <string name="catalyst_change_bundle_location_cancel" project="catalyst" translatable="false">Cancel</string>
+  <string name="catalyst_change_bundle_location_invalid" project="catalyst" translatable="false">Invalid bundler address: %1$s</string>
   <string name="catalyst_open_debugger_error" project="catalyst" translatable="false">Failed to open DevTools. Please check that the dev server is running and reload the app.</string>
   <string name="catalyst_debug_open" project="catalyst" translatable="false">Open DevTools</string>
   <string name="catalyst_performance_background" project="catalyst" translatable="false">Finish performance trace</string>