Note that the issue I had was with the EiffelTime, not EiffelStudio. And as a matter of fact I was not using EiffelStudio but another Eiffel compiler to compile this project with EiffelTime. I can confirm that adding the C flag -DWIN32_LEAN_AND_MEAN solves the problem. That being said, it would be nice to explain in the file eif_time.h itself why winsock2.h is used instead of winsock.h as suggested by Microsoft documentation. -- Eric Bezault