Socket don't close after close app

Hello, (sorry for my english)

I have a problem with sockets.

I have a flash application that is connected to my AIR application in local (I have no choice to use it). The flash App is a game and the AIR app is the launcher of the game. The game connect to the launcher by sockets and the launcher connect to my C# server by sockets too.

Then, my connection is right, if I don't start the game, I can connect and disconnect the launcher from the C# server without problems. But now, if I start the launcher, it connects to the server and start the game after authentification packets. After that, I can play to my game but if I close my launcher, the connection between the game and the launcher is close (I'm okay with it, that's what I wan't) but the C# server doesn't detect that the launcher is closed. If I close the flash app, the socket connection is closed immediatly.

Anybody can explain that ?

Thank's