Minecraft server connection errors and how to fix them

In short: Connection refused, Connection timed out and Unknown host mean the client never reached the server — it's down, the port is closed or not forwarded, or the address has a typo. Failed to verify username, Invalid session and Incompatible client mean the server answered but turned the player away: the Mojang account wasn't verified or the versions don't match. You are not white-listed, The server is full and You logged in from another location are server rules at work. Each one is below with its cause and fix.

How to read the error#

The game's own messages are translated into the player's language, while Java network errors are not: under the heading "Failed to connect to the server" you'll see a line like io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: <address> — Netty, the game's network library, appends the address the client tried to reach. Paper takes some messages from spigot.yml: they're in English by default whatever the client language, and you can rewrite them.

The other half of the picture is the server log, logs/latest.log. After startup it has the line Starting Minecraft server on *:25565: the asterisk means the server listens on every address of the machine, the number is the port. If you see **** FAILED TO BIND TO PORT! instead, the port is taken or server-ip holds an address that isn't yours — the Minecraft Wiki recommends leaving server-ip empty. Reading logs is covered in crash logs.

The client never reached the server#

Refused versus timed out tells you where to look. Per the Minecraft Wiki, refused means no process listens on the port and the operating system told the client so, while timed out means a firewall ignored the connection attempt. The Windows firewall and most home routers stay silent by default, so timed out is the one you'll see more often.

Step by step: where the connection breaks

1. 1

   The server listens on the port

   The log has the Starting Minecraft server on line, and on Linux ss -tlnp shows java on the right port. If not, the problem is the server itself, not the network.

2. 2

   Join from the same machine

   Use localhost (plus the port after a colon if it isn't 25565). If that works, the server is fine and the problem is the network.

3. 3

   Join from the same network

   Use the internal IP, something like 192.168.1.20 — see how to find your server IP. If that fails, it's the firewall on the server's computer.

4. 4

   Check from outside

   Use the online server status check or mobile data. If only outside access fails, it's port forwarding or ISP NAT. For a domain on a non-standard port, check the SRV record: the SRV record generator builds its fields.

# 1. the server listens on the port (Linux): a java process must show up
ss -tlnp | grep 25565

# 2. the line in logs/latest.log after startup
[Server thread/INFO]: Starting Minecraft server on *:25565

The server answered but turned the player away#

Which version to run so these errors are rare is covered in choosing a server version. ViaVersion ships a few days after a game update, so right after a new release Outdated server for players with an updated client is expected.

A server rule kicked in#

Errors on a Velocity network#

On a network the player connects to the proxy, and some errors come from Velocity itself. The texts are from its message file:

• Unable to connect you to <server>. Please try again later. — the proxy couldn't connect the player to a server from [servers]: it's off, still starting, or the address in velocity.toml is wrong.
• There are no available servers to connect you to. Try again later or contact an admin. — none of the servers in the try list answers.
• Your server did not send a forwarding request to the proxy. Make sure the server is configured for Velocity forwarding. — player info forwarding is off on the backend: set proxies.velocity.enabled: true in config/paper-global.yml.
• You are already connected to this proxy! — a second login with the same name. By default (kick-existing-players = false) Velocity refuses the new connection and leaves the first one alone.
• You are not logged into your Minecraft account. … — the proxy's counterpart of Failed to verify username with online-mode = true.

Proxy setup, the forwarding secret and the firewall for the servers behind it are in setting up Velocity.

Connection error or an anticheat punishment#

When a player says "I got kicked", first separate a network error from a punishment. The texts above come from the game, Paper and Velocity; an anticheat kick or ban shows up in its log. DGuard — the best anticheat for a modern Minecraft server — keeps a punishment log with reports in the panel when punishment-log: true is set in plugins/DGuard/config.yml: who was punished, when and for which cheat, with CSV export. If the player isn't in the log, look for the cause in the tables above.

The worst case is Connection refused for everyone because the server went down. The DGuard panel catches that too: if a server stays silent for 10 minutes, DGuard messages you and the team's admins in Telegram or by e-mail — and again when it comes back. DGuard opens no inbound ports and needs only outbound HTTPS; it works behind Velocity and BungeeCord and checks players on 1.21–26.x clients who join through ViaVersion exactly like everyone else.

FAQ#