Minecraft Connection Failures
Cannot Connect to Server
Example: "Internal Exception: java.io.IOException: An existing connection was forcibly closed by the remote host"
This error means you cannot connect; The server is offline, the traffic is being blocked, the server is rejecting the connection etc - You can't connect.
- Check the server is started to completition; The console will report "Done! X seconds" when it has fully started and is waiting for players.
- Check the server is responding: You can type commands such as "help" or "forge tps" in the console to see if the server responds to command input at all.
- Check your able to contact the server: If you are using the hostname, try using the numerical IP from the Server > Overview > Access menu (Legacy Panel: Virtual Server > sFTP/SSH Access). See: Connection Failures
Example: "[Netty Epoll Server IO #4/INFO] [FML]: Rejecting connection CLIENT: Compact Drawers: Requires version 1.12.2-18.104.22.168 but mod is not found on client."
Most Minecraft modpacks (excluding client-side-only mods) require that you are running the same version+build as you do on the server. This means if you are running for example "FTB Infinity Evolved 1.7.10, build 3.0.1" on the server and you attempt to connect with "FTB Infinity Evolved 1.7.10, build 3.0.2" the server may reject the connection. Mod rejection errors print to both server and client logs.
The server's installed version is usually visible above the "Overview/Console" menu (Old panel).
The new control panel (at the time of writing this) does not yet display installed versions, but you can still 'guestimate' which build is installed. Mod rejection errors will display both versions in conflict, first: the server version, secondly: the client version. As most build numbers tend to go up the numerical scale and not down, if the server shows a higher build number for a mod, it is likely the client is out of date - If the client shows a higher build number for a mod, it is likely the server is out of date.
You can change your installed server build via the "Versions" sub-menu for your Minecraft instance, alter mod builds directly via the "Mods" menu (Legacy Panel: "Mods Manager"), or alter the files directly via sFTP/SSH.
Note: It is recommended to change official mod packs via the "Versions" sub-menu first for your Minecraft instance. Any changes to the mods, without updating the configs, can result in odd server/gameplay behaviour; Versions will ensure your mod pack comes installed with all the 'trimmings' (configs, scripts etc) as intended.