I need to implement push notifications for my asp.net core project.For a news service
it needs to work in such a manner that if the user is not online while a message is being sent out, then the message will arrive at the client when they are online thenext time.
All the articles I can find about this, are all slightly vague about this case, and just emphasises the "real-time" communication.
So would it be possible to have push notifications that could that wiht signalr?
it needs to work in such a manner that if the user is not online while a message is being sent out, then the message will arrive at the client when they are online thenext time.
To achieve your above requirement, you can try:
mapping user to the connection id(s) and persist that mapping, which would help find/get new connection id(s) based on user name or email etc readable info after user connect/reconnect to hub, then you can send unread message/data to specific user by specifying connection id(s).
Note: you can also send a message to a specific user by passing the user identifier to the User function in a hub method, please refer to this doc: https://learn.microsoft.com/en-us/aspnet/core/signalr/groups?view=aspnetcore-5.0#users-in-signalr
for unread messages, as #SamiKuhmonen mentioned, you can store/persist those messages in somewhere, and if you want to persist information after restarts or you would host hub on multi-servers/instances, in-memory store is not a good approach. You can try to store messages in database etc permanent, external storage.
define and use a flag to indicates if the message has been seen by user. After client received a message, then invoke a hub method to update that flag or delete that message from the store.
Related
We are building an app with chat functionality in Flutter, and I have figured out almost everything about how it should be done, except how the notifications can be sent to only one device (Or possibly a few devices).
The best option so far is to send the notification to an FCM registration token since we use Firebase for all of our back-end, but I can't do that without knowing the token. And the only way I can know that is to store it in Firestore (For example the users document) and retrieve it when needed. Is this a good solution, and what happens if the registration token changes? Should I update the token every time the user opens the app to make sure that it is correct?
You don't need to store the token on the server, you just need to know who you are sending the message to. Just follow these steps
Client
1.a When you app starts, retrieve the token via getToken()
1.b Store it locally
1.c if it has changed, send it to a Cloud function, and register it to a topic or device group
1.d Dont forget to register to onTokenRefresh() to repeat 1.a-c for new tokens
Server
2.a Implement the function corresponding to 1.c
2.b When required, send messages to a topic or device group
I am doing an application in health in Nativescript and using https://github.com/EddyVerbruggen/nativescript-plugin-firebase
where I need to send a specific user a notification to alert him about something.
I have seen that to send to a specific device, the registration token can be used but is there any other way?
PS : when the user log in, I have an internal id that can be used to identify the user.
There is no other way to securely target an individual device. The registration token is the way the FCM identifies the device.
If you would like a non-secure way of delivering the message, you could try to use a uniquely named topic, but be aware that any device attached to your project will be able to listen to every topic if they just know the name.
I'm trying to send out an FCM message to a specific set of users (or really, a single user) based on a specific user property but looking through the FCM HTTP API I can't seem to find a way to do that. I can send to users via topics, registration tokens, and device group notification keys, but I don't have any of that infrastructure set up in the near term. I know this functionality exists as you can send such a message via the UI, but I'm not seeing how to do it in the API documentation as yet.
There is currently no parameter that you could use to specify a user property (or even for user segments) that will serve as a target for the FCM API to send the message to.
As you've already searched, the only targets possible are single/multiple registration tokens (to and registration_ids), topics, conditions, and device groups (notification_key).
The option you're looking for is currently only available when using the Notifications Console.
With Firebase Cloud Messaging for Web,
How do I maintain the list of valid tokens in my database? For example I've noticed when a user turns off notifications and revisits the site, a new token will be generated and the old token in my database is useless.
I've also tried using Firebase messaging.onTokenRefresh() callback, but it does not get called when I turned off notifications. Also in this case, even if it did get triggered, it returns a new token that was refreshed. How do I keep track of the old token that was refreshed?
Can someone please share with me their thoughts/ways to maintain and ensure the token list in the database are valid or up-to-date?
Any feedback is much appreciated.
Thank you,
Christina
messaging.onTokenRefresh() is probably a wrapper around the event onpushsubscriptionchange.
Indeed that event is currently only called when the subscription is enabled (or enabled again), but not when the permission for push notifications is revoked. So at the moment you can only know that an endpoint has expired when you try to send a notification to it.
More details:
http://blog.pushpad.xyz/2016/05/the-push-api-and-its-wild-unsubscription-mechanism/
In any case you can use the callback to send any new token to the server: at first you will have two tokens stored for the same browser, one expired and the other valid.
Some problems arise if you have data associated to the endpoint (e.g. tag) that you want to preserve during the endpoint change: see the blog post for some suggestions.
I'm trying to understand what I will need to build on my server for Push notifications to work successfully.
My thoughts were:
The phone sends the notify URL to my server
The server stores the information in a Database
A separate process or PHP script will query the database and open continuous looping process for each device. (Each socket will be querying a 3rd party API)
When there is a change detected in the API for that device a push notification will be sent to the device's notify url.
Is this the right method on what needs to be done. Isn't this going to eat up server resources or is it the expected outcome of Push a push notifications server?
I've produced a simple diagram on all this below:
First of all, let's separate the process in the main stages needed for PUSH.
Device subscription.
Send the PUSH
Process the notification on device.
Subscription
For the subscription, your device (more specifically, your App) must call the PUSH api,for enabling PUSH notifications. This call to the push API will give you a URL that uniquely identify the device where your application is installed and running. You should store this URL on your database, the same way you store a user's email, or a user's phone number. No special black magic here. You only use it when you need to send a communication to a user.
Send the PUSH
For the push stuff, the same approach as for email, or SMS messaging here: "One does not simply make an infinite loop and send a message if any change is detected". What you have to do is, just send the PUSH message when your application needs to. So you have the user to which you want to send a message, instead of opening a SMTP connection to send ane mail, just build the PUSH XML Message and call the URL associated with that user. Some things to consider here are:
Network reliability (you need to retry if you can't connect to the server).
Response error code-handling (you don't need to retry if the server tells you that the phone has uninstalled your application, for example).
Scalability. You don't want to send a PUSH message from your PHP code, because you don't know how long it will take for the task to be completed. You have to make this thing asynchronously. So just queue up all the push messages, you can create a separate process (windows service, nodeJS service, cron job, daemon, etc.) to send the PUSH, handle retries and errors and clean the queue.
Process the notification on Device
So now that you are this far, you need to handle the notification on the phone. It depends on the type of PUSH notification that you are sending:
Tile. You will update the image, text and counter of the application tile, if the user has put your application to the start screen. On client side you need nothing to so, as all these parameters are part of your PUSH request.
Toast. This one requires a title, text (limited to some 35 characters more or less) and a relative URL inside of your APP. Your application will be launched (like when you click on a Toast notification from Twitter, for example) using the URI that you specify in the payload. So a bit of data can be already injected here. You may/or may not make a request to your server for new data. It is up to you.
Raw. This one is pretty much silent. Is not seen by the user if your APP is not running. As you might guess, this kind of PUSH is useful to live update your running APP, instead of continuously polling your server, wasting user battery and bandwidth and wasting your server resources. You can send anything (raw bytes or strings) up to the max size of the payload allowed my Microsoft.
If yo have any more questions, don't hesitate to ask.
Bottom line: separate the PUSH sending, make it async, don't you ever forget that...
Your PHP script that continually pings the database for changes...THAT is what will eat up your system resources. Push notifications go hand in hand with Event Driven Programming. This means that ideally, your code shouldn't continuously ping your DB. Rather, when something happens (ie, an "event"), THEN your code does something...like contact your phone via push notification.
Your steps for push notifications are more or less correct, but are incomplete. Step 4: the server contacts the client via the notify url (which you have). Step 5 is that the client then contacts the server to actually pull down the information it needs. That is: The new information is not provided to the client via the notify url. Once the client has its new information, then the program continues as normal (populates a list, downloads skynet, etc.)
Your third step is very wasteful and not practical if your app is installed on more than a few devices.
Instead, each device should be subscribed to types of server updates it cares about. Your server's DB will have a mapping from each type of update you support to the list of notification channel URLs of devices that care about this update type.
When your server detects an update of type X, it would send a notification to all devices subscribed to that type of update.