I have been trying to read the official docs and guides about how to send message from one device to another. I have saved registration token of both devices in the Real Time Database, thus I have the registration token of another device.
I have tried the following way to send the message
RemoteMessage message = new RemoteMessage.Builder(getRegistrationToken())
.setMessageId(incrementIdAndGet())
.addData("message", "Hello")
.build();
FirebaseMessaging.getInstance().send(message);
However this is not working. The other device doesn't receive any message. I am not even sure, if I can use upstream message sending to conduct device to device communication.
PS: I just want to know if device-to-device messaging is possible using FCM? If yes, then is the code I used have some issue? If yes, then what is the correct way.
Update:
My question was to ask whether device to device messaging without using any separate server other than firebase could messaging is possible or not, if yes than how, since there's no documentation about it. I do not understand what is left to explain here? Anyways I got the answer and will update it as an answer once the question gets reopened.
Firebase has two features to send messages to devices:
the Notifications panel in your Firebase Console allows you to send notifications to specific devices, groups of users, or topics that users subscribed to.
by calling Firebase Cloud Messaging API, you can send messages with whatever targeting strategy you prefer. Calling the FCM API requires access to your Server key, which you should never expose on client devices. That's why you should always run such code on an app server.
The Firebase documentation shows this visually:
Sending messages from one device directly to another device is not supported through the Firebase Cloud Messaging client-side SDKs.
Update: I wrote a blog post detailing how to send notifications between Android devices using Firebase Database, Cloud Messaging and Node.js.
Update 2: You can now also use Cloud Functions for Firebase to send messages securely, without spinning up a server. See this sample use-case to get started. If you don't want to use Cloud Functions, you can run the same logic on any trusted environment you already have, such as your development machine, or a server you control.
Warning There is a very important reason why we don't mention this approach anywhere. This exposes your server key in the APK that
you put on every client device. It can (and thus will) be taken from
there and may lead to abuse of your project. I highly recommend
against taking this approach, except for apps that you only put on
your own devices. – Frank van Puffelen
Ok, so the answer by Frank was correct that Firebase does not natively support device to device messaging. However there's one loophole in that. The Firebase server doesn't identify whether you have send the request from an actual server or are you doing it from your device.
So all you have to do is send a Post Request to Firebase's messaging server along with the Server Key. Just keep this in mind that the server key is not supposed to be on the device, but there's no other option if you want device-to-device messaging using Firebase Messaging.
I am using OkHTTP instead of default way of calling the Rest API. The code is something like this -
public static final String FCM_MESSAGE_URL = "https://fcm.googleapis.com/fcm/send";
OkHttpClient mClient = new OkHttpClient();
public void sendMessage(final JSONArray recipients, final String title, final String body, final String icon, final String message) {
new AsyncTask<String, String, String>() {
#Override
protected String doInBackground(String... params) {
try {
JSONObject root = new JSONObject();
JSONObject notification = new JSONObject();
notification.put("body", body);
notification.put("title", title);
notification.put("icon", icon);
JSONObject data = new JSONObject();
data.put("message", message);
root.put("notification", notification);
root.put("data", data);
root.put("registration_ids", recipients);
String result = postToFCM(root.toString());
Log.d(TAG, "Result: " + result);
return result;
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(String result) {
try {
JSONObject resultJson = new JSONObject(result);
int success, failure;
success = resultJson.getInt("success");
failure = resultJson.getInt("failure");
Toast.makeText(getCurrentActivity(), "Message Success: " + success + "Message Failed: " + failure, Toast.LENGTH_LONG).show();
} catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getCurrentActivity(), "Message Failed, Unknown error occurred.", Toast.LENGTH_LONG).show();
}
}
}.execute();
}
String postToFCM(String bodyString) throws IOException {
RequestBody body = RequestBody.create(JSON, bodyString);
Request request = new Request.Builder()
.url(FCM_MESSAGE_URL)
.post(body)
.addHeader("Authorization", "key=" + SERVER_KEY)
.build();
Response response = mClient.newCall(request).execute();
return response.body().string();
}
I hope Firebase will come with a better solution in future. But till then, I think this is the only way. The other way would be to send topic message or group messaging. But that was not in the scope of the question.
Update:
The JSONArray is defined like this -
JSONArray regArray = new JSONArray(regIds);
regIds is a String array of registration ids, you want to send this message to. Keep in mind that the registration ids must always be in an array, even if you want it to send to a single recipient.
I have also been using direct device to device gcm messaging in my prototype. It has been working very well. We dont have any server. We exchange GCM reg id using sms/text and then communicate using GCM after that. I am putting here code related to GCM handling
**************Sending GCM Message*************
//Sends gcm message Asynchronously
public class GCM_Sender extends IntentService{
final String API_KEY = "****************************************";
//Empty constructor
public GCM_Sender() {
super("GCM_Sender");
}
//Processes gcm send messages
#Override
protected void onHandleIntent(Intent intent) {
Log.d("Action Service", "GCM_Sender Service Started");
//Get message from intent
String msg = intent.getStringExtra("msg");
msg = "\"" + msg + "\"";
try{
String ControllerRegistrationId = null;
//Check registration id in db
if(RegistrationIdAdapter.getInstance(getApplicationContext()).getRegIds().size() > 0 ) {
String controllerRegIdArray[] = RegistrationIdAdapter.getInstance(getApplicationContext()).getRegIds().get(1);
if(controllerRegIdArray.length>0)
ControllerRegistrationId = controllerRegIdArray[controllerRegIdArray.length-1];
if(!ControllerRegistrationId.equalsIgnoreCase("NULL")){
// 1. URL
URL url = new URL("https://android.googleapis.com/gcm/send");
// 2. Open connection
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// 3. Specify POST method
urlConnection.setRequestMethod("POST");
// 4. Set the headers
urlConnection.setRequestProperty("Content-Type", "application/json");
urlConnection.setRequestProperty("Authorization", "key=" + API_KEY);
urlConnection.setDoOutput(true);
// 5. Add JSON data into POST request body
JSONObject obj = new JSONObject("{\"time_to_live\": 0,\"delay_while_idle\": true,\"data\":{\"message\":" + msg + "},\"registration_ids\":[" + ControllerRegistrationId + "]}");
// 6. Get connection output stream
OutputStreamWriter out = new OutputStreamWriter(urlConnection.getOutputStream());
out.write(obj.toString());
out.close();
// 6. Get the response
int responseCode = urlConnection.getResponseCode();
BufferedReader in = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
String inputLine;
StringBuffer response = new StringBuffer();
while ((inputLine = in.readLine()) != null){
response.append(inputLine);
}
in.close();
Log.d("GCM getResponseCode:", new Integer(responseCode).toString());
}else{
Log.d("GCM_Sender:","Field REGISTRATION_TABLE is null");
}
}else {
Log.d("GCM_Sender:","There is no Registration ID in DB ,please sync devices");
}
} catch (Exception e) {
e.printStackTrace();
//MessageSender.getInstance().sendMessage(msg, Commands.SMS_MESSAGE);
}
}
//Called when service is no longer alive
#Override
public void onDestroy() {
super.onDestroy();
//Do a log that GCM_Sender service has been destroyed
Log.d("Action Service", "GCM_Sender Service Destroyed");
}
}
**************Receiving GCM Message*************
public class GCM_Receiver extends WakefulBroadcastReceiver {
public static final String RETRY_ACTION ="com.google.android.c2dm.intent.RETRY";
public static final String REGISTRATION ="com.google.android.c2dm.intent.REGISTRATION";
public SharedPreferences preferences;
//Processes Gcm message .
#Override
public void onReceive(Context context, Intent intent) {
ComponentName comp = new ComponentName(context.getPackageName(),
GCMNotificationIntentService.class.getName());
//Start GCMNotificationIntentService to handle gcm message asynchronously
startWakefulService(context, (intent.setComponent(comp)));
setResultCode(Activity.RESULT_OK);
/*//Check if DatabaseService is running .
if(!DatabaseService.isServiceRunning) {
Intent dbService = new Intent(context,DatabaseService.class);
context.startService(dbService);
}*/
//Check if action is RETRY_ACTION ,if it is then do gcm registration again .
if(intent.getAction().equals(RETRY_ACTION)) {
String registrationId = intent.getStringExtra("registration_id");
if(TextUtils.isEmpty(registrationId)){
DeviceRegistrar.getInstance().register(context);
}else {
//Save registration id to prefs .
preferences = PreferenceManager.getDefaultSharedPreferences(context);
SharedPreferences.Editor editor = preferences.edit();
editor.putString("BLACKBOX_REG_ID",registrationId);
editor.commit();
}
} else if (intent.getAction().equals(REGISTRATION)) {
}
}
}
//Processes gcm messages asynchronously .
public class GCMNotificationIntentService extends IntentService{
public static final int NOTIFICATION_ID = 1;
private NotificationManager mNotificationManager;
String gcmData;
private final String TAG = "GCMNotificationIntentService";
//Constructor with super().
public GCMNotificationIntentService() {
super("GcmIntentService");
}
//Called when startService() is called by its Client .
//Processes gcm messages .
#Override
protected void onHandleIntent(Intent intent) {
Log.d("GCMNotificationIntentService", "GCMNotificationIntentService Started");
Bundle extras = intent.getExtras();
//Get instance of GoogleCloudMessaging .
GoogleCloudMessaging gcm = GoogleCloudMessaging.getInstance(this);
//Get gcm message type .
String messageType = gcm.getMessageType(intent);
if (!extras.isEmpty()) {
if (GoogleCloudMessaging.MESSAGE_TYPE_SEND_ERROR
.equals(messageType)) {
sendNotification("Send error: " + extras.toString());
} else if (GoogleCloudMessaging.MESSAGE_TYPE_DELETED
.equals(messageType)) {
sendNotification("Deleted messages on server: "
+ extras.toString());
} else if (GoogleCloudMessaging.MESSAGE_TYPE_MESSAGE
.equals(messageType)) {
Log.i(TAG, "Completed work # " + SystemClock.elapsedRealtime());
gcmData = extras.getString("message");
Intent actionService = new Intent(getApplicationContext(),Action.class);
actionService.putExtra("data", gcmData);
//start Action service .
startService(actionService);
//Show push notification .
sendNotification("Action: " + gcmData);
//Process received gcmData.
Log.d(TAG,"Received Gcm Message from Controller : " + extras.getString("message"));
}
}
GCM_Receiver.completeWakefulIntent(intent);
}
//Shows notification on device notification bar .
private void sendNotification(String msg) {
mNotificationManager = (NotificationManager) this.getSystemService(Context.NOTIFICATION_SERVICE);
Intent notificationIntent = new Intent(this, BlackboxStarter.class);
//Clicking on GCM notification add new layer of app.
notificationIntent.setFlags( Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
PendingIntent contentIntent = PendingIntent.getActivity(this, 0,notificationIntent, PendingIntent.FLAG_CANCEL_CURRENT);
NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(
this).setSmallIcon(R.drawable.gcm_cloud)
.setContentTitle("Notification from Controller")
.setStyle(new NotificationCompat.BigTextStyle().bigText(msg))
.setContentText(msg);
mBuilder.setContentIntent(contentIntent);
mNotificationManager.notify(NOTIFICATION_ID, mBuilder.build());
//Play default notification
try {
Uri notification = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
Ringtone r = RingtoneManager.getRingtone(getApplicationContext(), notification);
r.play();
} catch (Exception e) {
e.printStackTrace();
}
}
//Called when service is no longer be available .
#Override
public void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
Log.d("GCMNotificationIntentService", "GCMNotificationIntentService Destroyed");
}
}
According to the new documentation which was updated on October 2, 2018 you must send post request as below
https://fcm.googleapis.com/fcm/send
Content-Type:application/json
Authorization:key=AIzaSyZ-1u...0GBYzPu7Udno5aA //Server key
{
"to": "sent device's registration token",
"data": {
"hello": "message from someone",
}
}
To get device's registration token extend FirebaseMessagingService and override onNewToken(String token)
For more info refer to doc https://firebase.google.com/docs/cloud-messaging/android/device-group
I am late but above solutions has helped me to write down this simple answer, you can send your message directly to android devices from android application, here is the simple implementation I have done and it works great for me.
compile android volley library
compile 'com.android.volley:volley:1.0.0'
Just copy paste this simple function ;) and your life will become smooth just like knife in butter. :D
public static void sendPushToSingleInstance(final Context activity, final HashMap dataValue /*your data from the activity*/, final String instanceIdToken /*firebase instance token you will find in documentation that how to get this*/ ) {
final String url = "https://fcm.googleapis.com/fcm/send";
StringRequest myReq = new StringRequest(Request.Method.POST,url,
new Response.Listener<String>() {
#Override
public void onResponse(String response) {
Toast.makeText(activity, "Bingo Success", Toast.LENGTH_SHORT).show();
}
},
new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(activity, "Oops error", Toast.LENGTH_SHORT).show();
}
}) {
#Override
public byte[] getBody() throws com.android.volley.AuthFailureError {
Map<String, Object> rawParameters = new Hashtable();
rawParameters.put("data", new JSONObject(dataValue));
rawParameters.put("to", instanceIdToken);
return new JSONObject(rawParameters).toString().getBytes();
};
public String getBodyContentType()
{
return "application/json; charset=utf-8";
}
#Override
public Map<String, String> getHeaders() throws AuthFailureError {
HashMap<String, String> headers = new HashMap<String, String>();
headers.put("Authorization", "key="+YOUR_LEGACY_SERVER_KEY_FROM_FIREBASE_CONSOLE);
headers.put("Content-Type","application/json");
return headers;
}
};
Volley.newRequestQueue(activity).add(myReq);
}
Note
If you want to send message to topics so you can change parameter instanceIdToken to something like /topics/topicName.
For groups implementation is the same but you just need to take care of parameters. checkout Firebase documentation and you can pass those parameters.
let me know if you face any issue.
I wanna send some DTO object to server. Server have "Valid" annotation, and when server getting not valid DTO, he should send validation errors and something like "HttpStatus.BAD_REQUEST", but when I'm trying to send HttpStatus.BAD_REQUEST doOnError just ignore it.
POST-request from client
BookDTO bookDTO = BookDTO
.builder()
.author(authorTf.getText())
.title(titleTf.getText())
.publishDate(LocalDate.parse(publishDateDp.getValue().toString()))
.owner(userAuthRepository.getUser().getLogin())
.fileData(file.readAllBytes())
.build();
webClient.post()
.uri(bookAdd)
.contentType(MediaType.APPLICATION_JSON)
.bodyValue(bookDTO)
.retrieve()
.bodyToMono(Void.class)
.doOnError(exception -> log.error("Error on server - [{}]", exception.getMessage()))
.onErrorResume(WebClientResponseException.class, throwable -> {
if (throwable.getStatusCode() == HttpStatus.BAD_REQUEST) {
log.error("BAD_REQUEST!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"); --My log doesn't contain this error, but server still has errors from bindingResult
return Mono.empty();
}
return Mono.error(throwable);
})
.block();
Server-part
#PostMapping(value = "/add", consumes = {MediaType.APPLICATION_JSON_VALUE})
public HttpStatus savingBook(#RequestBody #Valid BookDTO bookDTO, BindingResult bindingResult) {
List<FieldError> errors = bindingResult.getFieldErrors();
if (bindingResult.hasErrors()) {
for (FieldError error : errors ) {
log.info("Client post uncorrected data [{}]", error.getDefaultMessage());
}
return HttpStatus.BAD_REQUEST;
}else{libraryService.addingBookToDB(bookDTO);}
return null;
}
doOnError is a so-called side effect operation that could be used for instrumentation before onError signal is propagated downstream. (e.g. to log error).
To handle errors you could use onErrorResume. The example, the following code handles the WebClientResponseException and returns Mono.empty instead.
...
.retrieve()
.doOnError(ex -> log.error("Error on server: {}", ex.getMessage()))
.onErrorResume(WebClientResponseException.class, ex -> {
if (ex.getStatusCode() == HttpStatus.BAD_REQUEST) {
return Mono.empty();
}
return Mono.error(ex);
})
...
As an alternative as #Toerktumlare mentioned in his comment, in case you want to handle http status, you could use onStatus method of the WebClient
...
.retrieve()
.onStatus(HttpStatus.BAD_REQUEST::equals, res -> Mono.empty())
...
Update
While working with block it's important to understand how reactive signals will be transformed.
onNext(T) -> T in case of Mono and List<T> for Flux
onError -> exception
onComplete -> null, in case flow completes without onNext
Here is a full example using WireMock for tests
class WebClientErrorHandlingTest {
private WireMockServer wireMockServer;
#BeforeEach
void init() {
wireMockServer = new WireMockServer(wireMockConfig().dynamicPort());
wireMockServer.start();
WireMock.configureFor(wireMockServer.port());
}
#Test
void test() {
stubFor(post("/test")
.willReturn(aResponse()
.withHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
.withStatus(400)
)
);
WebClient webClient = WebClient.create("http://localhost:" + wireMockServer.port());
Mono<Void> request = webClient.post()
.uri("/test")
.retrieve()
.bodyToMono(Void.class)
.doOnError(e -> log.error("Error on server - [{}]", e.getMessage()))
.onErrorResume(WebClientResponseException.class, e -> {
if (e.getStatusCode() == HttpStatus.BAD_REQUEST) {
log.info("Ignoring error: {}", e.getMessage());
return Mono.empty();
}
return Mono.error(e);
});
Void response = request.block();
assertNull(response);
}
}
The response is null because we had just complete signal Mono.empty() that was transformed to null by applying block
How to achieve reactive message processing in Spring Cloud Stream? I read about Spring Cloud Function and that I should use them for reactive processing so I created sample one:
#Bean
public Consumer<Flux<Message<Loan>>> loanProcess() {
return loanMessages ->
loanMessages
.flatMap(loanMessage -> Mono.fromCallable(() -> {
if (loanMessage.getPayload().getStatus() == null) {
log.error("Empty status");
throw new RuntimeException("Loan status is empty");
}
return "Good";
}))
.doOnError(throwable -> log.error("Exception occurred: {}", throwable))
.subscribe(status -> log.info("Message processed correctly: {}", status));
}
Afterwards I started to thinking what is the difference between the above function and the class with #StreamListener and usage of Reactor types:
#StreamListener(Sink.INPUT)
public void loanReceived(Message<Loan> message) {
Mono.just(message)
.flatMap(loanMessage -> Mono.fromCallable(() -> {
if (loanMessage.getPayload().getStatus() == null) {
log.error("Empty status");
throw new RuntimeException("Loan status is empty");
}
log.info("Correct message");
return "Correct message received";
}))
.doOnError(throwable -> log.error("Exception occurred: {}", throwable.getClass()))
.subscribe(status -> log.info("Message processed correctly: {}", status));
}
Additionally, in Spring Webflux I understand that there are few threads from netty which handle requests processing (running in event loop). However, I cannot find a documentation how thread model works in Spring Cloud Stream.
I developed a project with Springboot and used Vertx as an asynchronous reactive toolkit. My ServerVerticle, create a httpServer which receives http requests from an Angular app and sends messages to it via eventBus. By the way, the time that received message arrives, ServerVerticle sends it to another verticle which has service instance in it (for connecting to repository). i tested it with postman and get "No handlers for address" error as a bad request.
here is my ServerVerticle:
HttpServerResponse res = routingContext.response();
res.setChunked(true);
EventBus eventBus = vertx.eventBus();
eventBus.request(InstrumentsServiceVerticle.FETCH_INSTRUMENTS_ADDRESS, "", result -> {
if (result.succeeded()) {
res.setStatusCode(200).write((Buffer) result.result().body()).end();
} else {
res.setStatusCode(400).write(result.cause().toString()).end();
}
});
My instrumentVerticle is as follows:
static final String FETCH_INSTRUMENTS_ADDRESS = "fetch.instruments.service";
// Reuse the Vert.x Mapper :)
private final ObjectMapper mapper = Json.mapper;
private final InstrumentService instrumentService;
public InstrumentsServiceVerticle(InstrumentService instrumentService) {
this.instrumentService = instrumentService;
}
private Handler<Message<String>> fetchInstrumentsHandler() {
return msg -> vertx.<String>executeBlocking(future -> {
try {
future.complete(mapper.writeValueAsString(instrumentService.getInstruments()));
} catch (JsonProcessingException e) {
logger.error("Failed to serialize result "+ InstrumentsServiceVerticle.class.getName());
future.fail(e);
}
},
result -> {
if (result.succeeded()) {
msg.reply(result.result());
} else {
msg.reply(result.cause().toString());
}
});
}
#Override
public void start() throws Exception {
super.start();
vertx.eventBus().<String>consumer(FETCH_INSTRUMENTS_ADDRESS).handler(fetchInstrumentsHandler());
}
and i deployed both verticles in the springbootApp starter.
I am using ReplyingKafkaTemplate to establish a synchronous call between two microservices.
The receiver of the event is annotated with SendTo as below:
#KafkaListener(topics = "${kafka.topic.prefix}"
+ "${kafka.topic.name}", containerFactory = "customEventKafkaListenerFactory")
#SendTo
public CustomResponseEvent onMessage(
#Payload #Valid CustomRequestEvent event, #Header(KafkaHeaders.CORRELATION_ID) String correlationId,
#Header(KafkaHeaders.REPLY_TOPIC) String replyTopic) {
//Making some REST API calls to another external system here using RestTemplate
}
The REST API call can throw a 4xx or 5xx. There are multiple such calls, some to internal systems, and some to external systems. It may be a bad design, but let's not get into that.
I would like to have a global exception handler for the RestTemplate where I can catch all the exceptions, and then return a response to the original sender of the event.
I am using the same replyTopic and correlationId as received in the consumer to publish the event.
But still the receiver of the response throws No pending reply exception.
Whatever approach I have above, is it possible to achieve such a central error response event publisher?
Is there any other alternative that is best suited for this exception handling?
The #KafkaListener comes with the:
/**
* Set an {#link org.springframework.kafka.listener.KafkaListenerErrorHandler} bean
* name to invoke if the listener method throws an exception.
* #return the error handler.
* #since 1.3
*/
String errorHandler() default "";
That one is used to catch and process all the downstream exceptions and if it returns a result, it is sent back to the replyTopic:
public void onMessage(ConsumerRecord<K, V> record, Acknowledgment acknowledgment, Consumer<?, ?> consumer) {
Message<?> message = toMessagingMessage(record, acknowledgment, consumer);
logger.debug(() -> "Processing [" + message + "]");
try {
Object result = invokeHandler(record, acknowledgment, message, consumer);
if (result != null) {
handleResult(result, record, message);
}
}
catch (ListenerExecutionFailedException e) { // NOSONAR ex flow control
if (this.errorHandler != null) {
try {
Object result = this.errorHandler.handleError(message, e, consumer);
if (result != null) {
handleResult(result, record, message);
}
}
catch (Exception ex) {
throw new ListenerExecutionFailedException(createMessagingErrorMessage(// NOSONAR stack trace loss
"Listener error handler threw an exception for the incoming message",
message.getPayload()), ex);
}
}
else {
throw e;
}
}
See RecordMessagingMessageListenerAdapter source code for more info.