FirebaseMessagingException: Connection refused on server

Environment:

* Firebase SDK version: 9.2.0
* Library version:
* Firebase Product: Firebase cloud messaging (FCM)

Problem:

I am having a problem using firebase admin sdk to send push notification from a java based web application.
When i run the code from localhost, everything is working and i was initialize the firebase app and send message.
But it is not working on the server.
I am getting following error.

Log:

10:40:24 com.google.firebase.messaging.FirebaseMessagingException: Unknown error while making a remote service call: Connection refused (Connection refused)
10:40:24 at com.google.firebase.messaging.FirebaseMessagingException.withMessagingErrorCode(FirebaseMessagingException.java:51)
10:40:24 at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1306)
10:40:24 at com.google.firebase.messaging.FirebaseMessagingClientImpl$MessagingErrorHandler.createException(FirebaseMessagingClientImpl.java:293)
10:40:24 at com.google.firebase.messaging.FirebaseMessagingClientImpl$MessagingErrorHandler.createException(FirebaseMessagingClientImpl.java:282)
10:40:24 at com.google.firebase.internal.AbstractHttpErrorHandler.handleIOException(AbstractHttpErrorHandler.java:63)
10:40:24 at com.google.firebase.internal.ErrorHandlingHttpClient.send(ErrorHandlingHttpClient.java:110)
10:40:24 at com.google.firebase.internal.ErrorHandlingHttpClient.sendAndParse(ErrorHandlingHttpClient.java:72)
10:40:24 at com.google.firebase.messaging.FirebaseMessagingClientImpl.sendSingleRequest(FirebaseMessagingClientImpl.java:127)
10:40:24 at com.google.firebase.messaging.FirebaseMessagingClientImpl.send(FirebaseMessagingClientImpl.java:113)
10:40:24 at com.google.firebase.messaging.FirebaseMessaging$1.execute(FirebaseMessaging.java:141)
10:40:24 at com.google.firebase.messaging.FirebaseMessaging$1.execute(FirebaseMessaging.java:138)
10:40:24 at com.google.firebase.internal.CallableOperation.call(CallableOperation.java:36)
10:40:24 at com.google.firebase.messaging.FirebaseMessaging.send(FirebaseMessaging.java:108)
10:40:24 at com.google.firebase.messaging.FirebaseMessaging.send(FirebaseMessaging.java:90)
10:40:24 at firebase.actions.JA_SendFirebaseMessage.sendFCMMessage(JA_SendFirebaseMessage.java:91)
10:40:24 at firebase.actions.JA_SendFirebaseMessage.executeAction(JA_SendFirebaseMessage.java:57)
10:40:24 at firebase.actions.JA_SendFirebaseMessage.executeAction(JA_SendFirebaseMessage.java:30)
10:40:24 at com.mendix.systemwideinterfaces.core.UserAction.execute(UserAction.java:58)
10:40:24 at com.mendix.basis.actionmanagement.CoreActionHandlerImpl.doCall(CoreActionHandlerImpl.scala:71)
10:40:24 at com.mendix.basis.actionmanagement.CoreActionHandlerImpl.call(CoreActionHandlerImpl.scala:48)
10:40:24 at com.mendix.core.actionmanagement.internal.InternalCoreAction.call(InternalCoreAction.java:57)
10:40:24 at com.mendix.basis.actionmanagement.ActionManager.$anonfun$executeSync$2(ActionManager.scala:104)
10:40:24 at com.mendix.util.classloading.Runner$.withContextClassLoader(Runner.scala:20)
10:40:24 at com.mendix.basis.actionmanagement.ActionManager.executeSync(ActionManager.scala:103)
10:40:24 at com.mendix.basis.actionmanagement.UserActionCallBuilderImpl.execute(UserActionCallBuilderImpl.scala:57)
10:40:24 at com.mendix.modules.microflowengine.actions.actioncall.ForegroundJavaAction.doExecute(ForegroundJavaAction.scala:35)
10:40:24 at com.mendix.modules.microflowengine.actions.actioncall.ForegroundJavaAction.doExecute(ForegroundJavaAction.scala:11)
10:40:24 at com.mendix.modules.microflowengine.actions.actioncall.JavaAction.execute(JavaAction.scala:38)
10:40:24 at com.mendix.modules.microflowengine.microflow.impl.MicroflowObject.$anonfun$execute$1(MicroflowObject.scala:32)
10:40:24 at scala.Option.flatMap(Option.scala:283)
10:40:24 at com.mendix.modules.microflowengine.microflow.impl.MicroflowObject.execute(MicroflowObject.scala:29)
10:40:24 at com.mendix.modules.microflowengine.microflow.impl.MicroflowImpl.executeAfterBreakingIfNecessary(MicroflowImpl.scala:176)
10:40:24 at com.mendix.modules.microflowengine.microflow.impl.MicroflowImpl.executeAction(MicroflowImpl.scala:116)
10:40:24 at com.mendix.systemwideinterfaces.core.UserAction.execute(UserAction.java:58)
10:40:24 at com.mendix.basis.actionmanagement.CoreActionHandlerImpl.doCall(CoreActionHandlerImpl.scala:71)
10:40:24 at com.mendix.basis.actionmanagement.CoreActionHandlerImpl.call(CoreActionHandlerImpl.scala:48)
10:40:24 at com.mendix.core.actionmanagement.internal.InternalCoreAction.call(InternalCoreAction.java:57)
10:40:24 at com.mendix.basis.actionmanagement.ActionManager.$anonfun$executeSync$2(ActionManager.scala:104)
10:40:24 at com.mendix.util.classloading.Runner$.withContextClassLoader(Runner.scala:20)
10:40:24 at com.mendix.basis.actionmanagement.ActionManager.executeSync(ActionManager.scala:103)
10:40:24 at com.mendix.basis.actionmanagement.MicroflowCallBuilderImpl.execute(MicroflowCallBuilderImpl.scala:62)
10:40:24 at com.mendix.webui.actions.client.MicroflowRuntimeOperationExecutor.runMicroflow(MicroflowRuntimeOperationExecutor.scala:97)
10:40:24 at com.mendix.webui.actions.client.MicroflowRuntimeOperationExecutor.$anonfun$apply$5(MicroflowRuntimeOperationExecutor.scala:57)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction$Helpers$.$anonfun$liftEither$1(RegularClientAction.scala:30)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction$Helpers$StateHandler.$anonfun$apply$4(RegularClientAction.scala:56)
10:40:24 at com.mendix.webui.requesthandling.helpers.StateHandling.withState(StateHandling.scala:46)
10:40:24 at com.mendix.webui.requesthandling.helpers.StateHandling.withState$(StateHandling.scala:43)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction$Helpers$StateHandler.withState(RegularClientAction.scala:46)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction$Helpers$StateHandler.apply(RegularClientAction.scala:54)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction$Helpers$StateHandler.apply(RegularClientAction.scala:46)
10:40:24 at com.mendix.webui.actions.client.MicroflowRuntimeOperationExecutor.apply(MicroflowRuntimeOperationExecutor.scala:58)
10:40:24 at com.mendix.webui.actions.client.RuntimeOperationAction.$anonfun$apply$1(RuntimeOperationAction.scala:49)
10:40:24 at scala.util.Either.flatMap(Either.scala:352)
10:40:24 at com.mendix.webui.actions.client.RuntimeOperationAction.apply(RuntimeOperationAction.scala:33)
10:40:24 at com.mendix.webui.actions.client.RuntimeOperationAction.apply(RuntimeOperationAction.scala:22)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction$Helpers$.$anonfun$liftEither$1(RegularClientAction.scala:30)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction.$anonfun$execute$3(RegularClientAction.scala:120)
10:40:24 at scala.util.Try$.apply(Try.scala:210)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction.$anonfun$execute$2(RegularClientAction.scala:120)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction.$anonfun$execute$2$adapted(RegularClientAction.scala:118)
10:40:24 at com.mendix.webui.requesthandling.helpers.ContextHandling.$anonfun$inContext$7(ContextHandling.scala:59)
10:40:24 at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
10:40:24 at com.mendix.basis.actionmanagement.ActionMonitoring$.$anonfun$monitor$1(ActionMonitoring.scala:52)
10:40:24 at com.mendix.util.classloading.Runner$.withContextClassLoader(Runner.scala:20)
10:40:24 at com.mendix.basis.actionmanagement.ActionMonitoring$.monitor(ActionMonitoring.scala:52)
10:40:24 at com.mendix.webui.requesthandling.helpers.ContextHandling.inContext(ContextHandling.scala:59)
10:40:24 at com.mendix.webui.requesthandling.helpers.ContextHandling.inContext$(ContextHandling.scala:33)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction.inContext(RegularClientAction.scala:94)
10:40:24 at com.mendix.webui.requesthandling.helpers.ContextHandling.inContext(ContextHandling.scala:30)
10:40:24 at com.mendix.webui.requesthandling.helpers.ContextHandling.inContext$(ContextHandling.scala:22)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction.inContext(RegularClientAction.scala:94)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction.$anonfun$execute$1(RegularClientAction.scala:118)
10:40:24 at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
10:40:24 at com.mendix.webui.requesthandling.helpers.ProfileHandling.profileRequest(ProfileHandling.scala:14)
10:40:24 at com.mendix.webui.requesthandling.helpers.ProfileHandling.profileRequest$(ProfileHandling.scala:10)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction.profileRequest(RegularClientAction.scala:94)
10:40:24 at com.mendix.webui.actions.client.RegularClientAction.execute(RegularClientAction.scala:115)
10:40:24 at com.mendix.webui.requesthandling.ClientRequestHandler.handleAction(ClientRequestHandler.scala:96)
10:40:24 at com.mendix.webui.requesthandling.ClientRequestHandler.processRequest(ClientRequestHandler.scala:69)
10:40:24 at com.mendix.externalinterface.connector.RequestHandler.doProcessRequest(RequestHandler.java:37)
10:40:24 at com.mendix.external.connector.MxRuntimeConnector.$anonfun$processRequest$1(MxRuntimeConnector.scala:54)
10:40:24 at com.mendix.external.connector.MxRuntimeConnector.$anonfun$processRequest$1$adapted(MxRuntimeConnector.scala:54)
10:40:24 at com.mendix.util.classloading.Runner$.withContextClassLoader(Runner.scala:20)
10:40:24 at com.mendix.external.connector.MxRuntimeConnector.processRequest(MxRuntimeConnector.scala:54)
10:40:24 at com.mendix.basis.impl.MxRuntimeImpl.processRequest(MxRuntimeImpl.scala:218)
10:40:24 at com.mendix.m2ee.appcontainer.server.handler.RuntimeServlet.service(RuntimeServlet.scala:40)
10:40:24 at javax.servlet.http.HttpServlet.service(HttpServlet.java:750)
10:40:24 at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:764)
10:40:24 at org.eclipse.jetty.servlet.ServletHandler$ChainEnd.doFilter(ServletHandler.java:1665)
10:40:24 at org.eclipse.jetty.websocket.servlet.WebSocketUpgradeFilter.doFilter(WebSocketUpgradeFilter.java:170)
10:40:24 at org.eclipse.jetty.servlet.FilterHolder.doFilter(FilterHolder.java:202)
10:40:24 at org.eclipse.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1635)
10:40:24 at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:527)
10:40:24 at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:221)
10:40:24 at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1570)
10:40:24 at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:221)
10:40:24 at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1384)
10:40:24 at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:176)
10:40:24 at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:484)
10:40:24 at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1543)
10:40:24 at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:174)
10:40:24 at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:129)
10:40:24 at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:122)
10:40:24 at org.eclipse.jetty.server.Server.handle(Server.java:563)
10:40:24 at org.eclipse.jetty.server.HttpChannel$RequestDispatchable.dispatch(HttpChannel.java:1598)
10:40:24 at org.eclipse.jetty.server.HttpChannel.dispatch(HttpChannel.java:753)
10:40:24 at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:501)
10:40:24 at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:282)
10:40:24 at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:314)
10:40:24 at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:100)
10:40:24 at org.eclipse.jetty.io.SelectableChannelEndPoint$1.run(SelectableChannelEndPoint.java:53)
10:40:24 at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.runTask(AdaptiveExecutionStrategy.java:421)
10:40:24 at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.consumeTask(AdaptiveExecutionStrategy.java:390)
10:40:24 at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.tryProduce(AdaptiveExecutionStrategy.java:277)
10:40:24 at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.run(AdaptiveExecutionStrategy.java:199)
10:40:24 at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:411)
10:40:24 at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:969)
10:40:24 at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.doRunJob(QueuedThreadPool.java:1194)
10:40:24 at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:1149)
10:40:24 at java.base/java.lang.Thread.run(Unknown Source)
10:40:24 Caused by: java.net.ConnectException: Connection refused (Connection refused)
10:40:24 at java.base/java.net.PlainSocketImpl.socketConnect(Native Method)
10:40:24 at java.base/java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
10:40:24 at java.base/java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
10:40:24 at java.base/java.net.AbstractPlainSocketImpl.connect(Unknown Source)
10:40:24 at java.base/java.net.SocksSocketImpl.connect(Unknown Source)
10:40:24 at java.base/java.net.Socket.connect(Unknown Source)
10:40:24 at java.base/sun.security.ssl.SSLSocketImpl.connect(Unknown Source)
10:40:24 at java.base/sun.net.NetworkClient.doConnect(Unknown Source)
10:40:24 at java.base/sun.net.www.http.HttpClient.openServer(Unknown Source)
10:40:24 at java.base/sun.net.www.http.HttpClient.openServer(Unknown Source)
10:40:24 at java.base/sun.net.www.protocol.https.HttpsClient.(Unknown Source)
10:40:24 at java.base/sun.net.www.protocol.https.HttpsClient.New(Unknown Source)
10:40:24 at java.base/sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(Unknown Source)
10:40:24 at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect0(Unknown Source)
10:40:24 at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
10:40:24 at java.base/sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source)
10:40:24 at java.base/sun.net.www.protocol.http.HttpURLConnection.getOutputStream0(Unknown Source)
10:40:24 at java.base/sun.net.www.protocol.http.HttpURLConnection.getOutputStream(Unknown Source)
10:40:24 at java.base/sun.net.www.protocol.https.HttpsURLConnectionImpl.getOutputStream(Unknown Source)
10:40:24 at com.google.api.client.http.javanet.NetHttpRequest.execute(NetHttpRequest.java:113)
10:40:24 at com.google.api.client.http.javanet.NetHttpRequest.execute(NetHttpRequest.java:84)
10:40:24 at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1012)
10:40:24 at com.google.firebase.internal.ErrorHandlingHttpClient.send(ErrorHandlingHttpClient.java:96)
10:40:24 ... 115 more

Code:

Initialising firebase app

`if(FirebaseApp.getApps().isEmpty())
{
FirebaseOptions options = FirebaseOptions.builder().setCredentials(GoogleCredentials.fromStream(serviceAccountKeyFileStream)).build();
try {
FirebaseApp.initializeApp(options);
} catch (Exception e) {
logger.info("FirebaseApp initialised failed.");
throw new com.mendix.systemwideinterfaces.MendixRuntimeException("Initialising FirebaseApp failed.\n"+e);
}
}`

Sending message

`Message message = Message.builder()
.putData("title", firebaseMessage.getTitle())
.putData("body", firebaseMessage.getBody())
.putData("url", firebaseMessage.getUrl())
.setToken(firebaseMessage.getToken())
.build();

var messagingInstance = FirebaseMessaging.getInstance();
var response = messagingInstance.send(message);`

Bắt đầu bằng cách xác định kết nối đi ra được thực hiện bởi FirebaseMessagingClientImpl.sendSingleRequest và so sánh các môi trường localhost và máy chủ; issue cung cấp stack trace liên quan và báo cáo Firebase Admin SDK 9.2.0. Kiểm tra quyền truy cập mạng của máy chủ đến dịch vụ FCM từ xa và xem vấn đề này có thể tái hiện bằng một lần gửi tối thiểu hay không. Hoàn tất nghĩa là xác định liệu lỗi có phải do môi trường hay do lỗi trong SDK gây ra, đồng thời ghi lại một cách khắc phục có thể tái hiện.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.