Simulink Winsock linker problem

Hi all, We are implementing a simple TCP/IP communication block in Simulink.

To this purpose we wrote an S-Function that we compile successfully with the following command: >> mex -O mytcpip.c WS2_32.lib -DWIN32

When we build the relevant model, the RTW generation code fails with the following log:

C:\Programmi\MATLAB7\work\xnet_grt_rtw>"C:\Programmi\MATLAB7\rtw\bin\win32\gmake" -f xnet.mk ADD_MDL_NAME_TO_GLOBALS=1 C:\Programmi\MATLAB7\sys\lcc\bin\lcc -c -Foxnet.obj -DUSE_RTMODEL -DMODEL=xnet -DRT -DNUMST=1 -DTID01EQ=0 -DNCSTATES=0 -DMT=0 -DHAVESTDIO -I. -I.. -IC:\Programmi\MATLAB7\simulink\include -IC:\Programmi\MATLAB7\extern\include -IC:\Programmi\MATLAB7\rtw\c\src -IC:\Programmi\MATLAB7\rtw\c\libsrc -IC:\Programmi\MATLAB7\rtw\c\src\ext_mode\common -IC:\Programmi\MATLAB7\rtw\c\src\ext_mode\tcpip -IC:\Programmi\MATLAB7\rtw\c\src\ext_mode\serial -IC:\Programmi\MATLAB7\rtw\c\src\ext_mode\custom -Ic:\programmi\matlab7\work -Ic:\programmi\matlab7\work\xnet_grt_rtw -Ic:\programmi\matlab7\rtw\c\libsrc -IC:\Programmi\MATLAB7\sys\lcc\include -noregistrylookup xnet.c C:\Programmi\MATLAB7\sys\lcc\bin\lcc -c -Fort_nonfinite.obj -DUSE_RTMODEL -DMODEL=xnet -DRT -DNUMST=1 -DTID01EQ=0 -DNCSTATES=0 -DMT=0 -DHAVESTDIO -I. -I.. -IC:\Programmi\MATLAB7\simulink\include -IC:\Programmi\MATLAB7\extern\include -IC:\Programmi\MATLAB7\rtw\c\src -IC:\Programmi\MATLAB7\rtw\c\libsrc -IC:\Programmi\MATLAB7\rtw\c\src\ext_mode\common -IC:\Programmi\MATLAB7\rtw\c\src\ext_mode\tcpip -IC:\Programmi\MATLAB7\rtw\c\src\ext_mode\serial -IC:\Programmi\MATLAB7\rtw\c\src\ext_mode\custom -Ic:\programmi\matlab7\work -Ic:\programmi\matlab7\work\xnet_grt_rtw -Ic:\programmi\matlab7\rtw\c\libsrc -IC:\Programmi\MATLAB7\sys\lcc\include -noregistrylookup rt_nonfinite.c C:\Programmi\MATLAB7\sys\lcc\bin\lcclnk -s -LC:\Programmi\MATLAB7\sys\lcc\lib -o ../xnet.exe xnet.obj rt_nonfinite.obj grt_main.obj rt_sim.obj mytcpip.obj C:\Programmi\MATLAB7\rtw\c\lib\win32\rtwlib_lcc.lib mytcpip.obj .text: undefined reference to '_WSAStartup@8'

Build error: Error using ==> RTW.makertw.make_rtw Error using ==> rtw_c Error(s) encountered while building model "xnet"

Model error: Error building Real-Time Workshop target for block diagram 'xnet'. MATLAB error message: Error using ==> slbuild Error using ==> RTW.makertw.make_rtw Error using ==> rtw_c Error(s) encountered while building model "xnet"

Any suggestion?

Tnx