If you genuinely love Terraria and want to experience the incredible creativity of its modding community (Calamity alone offers 40+ hours of new content), do the right thing:
To get tModLoader working on a cracked 1449, you need this specific historical version: (the final 1.3.5.3 compatible build).
Unless the person you are playing with has the exact same crack, the exact same mod list, and has disabled Steam authentication in the serverconfig.txt , you will not connect. Even then, desyncs happen every 5 minutes.
but are:
Modern versions of tModLoader rely almost exclusively on the Steam Workshop for downloading, updating, and managing mods.