Oh, there's an article about that. Who'd have thought it.
"Windows 3.11 was released on November 8, 1993. It did not add any feature improvements over Windows 3.1; it only corrected problems."
"Windows for Workgroups 3.1 (originally codenamed Winball and later Sparta), released in October 1992, is an extended version of Windows 3.1 that features native networking support. It comes with SMB file sharing support via NetBIOS-based NBF and/or IPX network transport protocols"
"Windows for Workgroups 3.11 (originally codenamed Snowball) was released on August 11, 1993, and shipped in November 1993."
"A Winsock package was required to support TCP/IP networking in Windows 3.x. Usually third-party packages were used, but in August 1994, Microsoft released an add-on package (codenamed Wolverine) that provided TCP/IP support in Windows for Workgroups 3.11."