undefined reference to `WinMain@16'

**** Internal Builder is used for build               ****
gcc -O0 -g3 -Wall -c -fmessage-length=0 -oserver.o ..\server.c
gcc -otcpsrv.exe server.o -lws2_32
d:/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libmingw32.a(main.o):main.c:(.text+0xd2): undefined reference to `WinMain@16'
collect2: ld returned 1 exit status
Build error occurred, build is stopped
Time consumed: 1013  ms. 

原因，没写main函数...