Quick answer: Terraria dedicated listens on TCP 7777, needs little RAM and optional tShock for plugins.
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Frequently asked questions (FAQ)
Which port for Terraria?
Default 7777 TCP. UDP rarely needed. Firewall and panel port must match.
Vanilla or tShock?
Vanilla = official dedicated. tShock = plugins, ranks, anti-cheat. Clients then need a matching tShock-compatible version.
RAM?
2 GB often covers 8 players. Large worlds + many NPCs: 4 GB.