Server to client notification

[RockyM]

What is the best way of implementing server-to-client notifications in client(Rsessionbase)-server(CServer2) architecture. I know this can be done using asynchronous request from client to server, but is there any way that server can notify the client without client's explicit request.

[symbianyucca]

Maybe you could try using property monitoring.

[RockyM]

Could you please provide some information about monitoring you suggested (which class is that), some documentation or an example that I could look at.

[symbianyucca]

you could use RProperty API, just defined your property in the server, and use the Subscribe() function on the client side to get notifications on the changes.

[RockyM]

If I am right, this is Publish & Subscribe mechanism.

[hotcheese]

If I am right, this is Publish & Subscribe mechanism.

Yes.

It depends what you mean by 'explicit request'. There are several options for a client to be informed when the server has some information to push to it
- the client passes a TRequestStatus and whenever the server has information to notifity the client of it signals the status.
- the client passes a callback to the server (not directly, a callback can't go across the IP boundary, but it passes one to the client side proxy of the server)
- the client subscribes to something from publish and subscribe


However all 3 of these require the client doing something first, and have an element of the waiting for something (even if that waiting is done in parallel to performing some other actions). P&S is the one where the client is most decoupled from the server, but if its your server and your client, is decoupling to that extent necessary?

There's more mechanisms if you want, a message queue for example. But better for you to state your precise requriements first if none of the above is sufficient.

[RockyM]

The client and server run in separate processes. The most of the time client makes the requests and server responses to that requests. But sometimes server has to inform the client about some change (some data that server monitors have been changed). What is the most appropriate way of doing this? Is there some mechanism of notifications to which the client could subscribe, so that every time the change happens, the client is being informed, without reissuing request?
Examples are appreciated also.

[symbianyucca]

What would be wrong with the method I already suggested ?, did you try it ?

[hotcheese]

..Is there some mechanism of notifications to which the client could subscribe....

maybe there was a clue in one of the precise words your choose that should indicate yucca has already given you the answer?