Yes it is VisiBroker for Net.
The application is hosted by Excel. The user may login/logout or switch from server (using the CNS). When the user logout, he may keep Excel running. In that case, the TCP/IP connection stills alive until he left Excel. Same way, if he switch from server, Excel will keep one connection alive by ever used server.
If i just use an "idle timeout", the connection pool will perfectly work, and will re-establish a physical connection when needed. But, it that case, the code will have to run again a full initialization (about 40 seconds) because the application isn't stateless (many types, for which we need to get new references within the connection).
Anyway pinging the server, and setting an idle timeout higher than the ping period should work.
Thanks for your help