Minecraft server won't start – first steps?

Read logs/latest.log, check Java version (17+), eula.txt true, enough RAM (-Xmx), port 25565 open in firewall.

Connection timed out despite running server?

Firewall (UFW + provider), wrong IP, SRV not propagated yet, server binds localhost only (leave server-ip= empty).

UnsupportedClassVersionError – what does it mean?

Java too old. Minecraft 1.20+ needs Java 17 or 21. Check java -version and update.

Minecraft Server Won't Start – Check Java, EULA, Port & Logs

Quick answer: If the server won't run, read logs/latest.log. Top 3 causes: wrong Java version, eula.txt not accepted, port/firewall blocking.

If you landed here: Jar won't start, crashes immediately or players get "Connection timed out".

Error → cause → fix

Symptom / log	Cause	Fix
Server stops immediately	EULA not accepted	`eula.txt` → `eula=true`
UnsupportedClassVersionError	Java too old	Install Java 17
Connection timed out	Firewall	UFW 25565
Domain timeout	DNS/SRV	SRV record

Full setup: Install Minecraft server

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