License server via TCP connections

Hello,

I need to add some floating license to an application. What i want to do is making a license server which will be a windows service.
When the application (which is shared on a server) starts it will connect to the License Server. The License Server will check the number of client running and tell the new started client that it can be started or not.

In this way it is easy to change the license system of an application later.

Is this a good practice to do? If some guys have better ideas, let me know!

The problem i have with the TCP connections is that i'm not able to check the state of the connection between the server and the new client when a client is unexpected shutdown.
A client needs to be removed from the running list in the license server when i a client shutdown. Sometimes is it not possible to close the TCP connection properly when the client raises an error.

I was also thinking about broadcasting a packet to all clients in the running list of the license server. The clients which response to the broadcast are active. The other clients are inactive and can be removed from the running list.

I can't find out how to implement these things..
I currently have a simple TCP server with client. The client can perfectly communicate to the server but i'm not able to get the server updating the list of the active clients.

I hope you guys can give me some good idea's or some ways to do it!

Thx,
Lightbeam