There is no native TCP/IP support in Windows 3.1. There is no NETBIOS/NETBEUI support in WIndows 3.1. You have to purchase or sownload "Packet Drivers" (Clarkson are/were free and the most popular).
If you have Windows For Workgroups, then there was some network support included, Netbeui "fer sher", and maybe TCP/IP as well.
If you can find a copy, Netmanage Chameleon was a great package (used to be expensive), they have/had packages ranging from basic IP connectivity (with FTP, GOPHER, WAIS, etc) up to X-Windows support (with all the other utilities).
You might be better off loading a copy of Windows 95 (maybe 98), if you can find it. It operates with small RAM models and slower procesors. It also includes all the network connectivity.
Good Luck
Scott