Probably was "Windows 3.11, For Workgroups" as iirc Windows 3.1 didn't ship with a TCP/IP stack

There was a sockets API though (https://en.wikipedia.org/wiki/Winsock) and IIRC we all used Trumpet Winsock on Windows 3.1 with our dialup connections. But could have been 3.11 - my memory is a bit hazy.