Xvnc dies after the close of the client

[fusillo]

Hello i tested vnc-4_1_2-x86_linux on a linux server, when i try to 
connect from another pc with windows xp with the binary 
vnc-P4_2_8-x86_win32_viewer.exe i get the right xwindow session with my 
window manager, no error in the log nuvola:1.log, no problem with the 
ssh tunnel with putty, as soon as i close the window of the client on xp 
desktop i get the server is killed too with the log message:
X connection to :1.0 broken (explicit kill or server shutdown).
X connection to :1.0 broken (explicit kill or server shutdown).
xterm:  fatal IO error 32 (Pipe interrotta) or KillClient on X server ":1.0"
The last line is result from the broken of the server.
Why the Xvnc process dies? Is that the right behavior? Is it depended on 
   another enviroment setting?

Regards