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.