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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Frequently asked questions (FAQ)
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.