Question

Greetings,
in our company we are developing wcf service. This is used as a server and it works quite well. Hover there is a wish from customer that after they login to application they would like to see which users are logged in too.
I read about CallbackContract (based on some wcf chat application). How can we achive this goal?

Answer 1

Similar question asked here

You can deffinetly manage the logged users inside the server. I have created a personal pattern for dealing with such situations, and it ussually goes like this:

• create a client class inside the WCF server that will hold all the needed information about the client.

• create 2 methods in the service: logIn, logOut. the login method should be able to gather all the informations about the client that you want to store. Make sure to define properties that can uniquely identify a client instance. When the client conencts to the server it calls the login method, allowing the server to gather and save the information from the client. If using callbacks, this is the place to save the CallBack context object, in the client obejt. You can now save the Client object in the WCF server instance (I use a dictioary). When the client logs out, it calls the log out method and the server removes the entry.

• create a KeepAlive method in the server that regularry checks the connected clients to see if they are still connected (in case of network failure or app crash a client may not call the logout method).

I think this is the simplest way (not
saying it’s the best) to manage
clients in the server. There is no
problem with having multiple clients
from the same computer (you save the
Context when a client logges in) as
long as you have a way of uniquely
identify clients.

As for your last question, having
multiple services should not be a
problem. In fact you have the same WCF
server with different contracts (and
endpoints) for the different services
you offer. ALl the contracts reside in
the same WCF server instance so they
all can access the connected client
list.

If you have further questions, I would
be happy to answer them.

You can find the code you need to actually build the WCF service you require here