Requests/responses for help in this thread will be deleted. This thread covers many of the common problems you may have when running a server. Solutions included here are tried and true. Please read this list first before posting a new help thread. Help, Someone has logged in as me! Make sure your server.properties has online-mode=true Offline mode servers will get no support. There is only one good way to protect your server, and that is by running online-mode=true. Error: java.lang.NoClassDefFoundError: Could not initialize class org.fusesource.jansi.internal.kernel32 Full error: java.lang.NoClassDefFoundError: Could not initialize class org.fusesource.jansi.internal.kernel32 at org.fusesource.jansi.internal.WindowsSupport.getConsoleMode<WindowsSupport.java:50 at jline.WindowsTerminal.getConsoleMode<WindowsTerminal.java:176> at jline.WindowsTerminal.init<WindowsTerminal.java"80> at jline.TerminalFactory.create<Terminalfactory.java:93> at jline.TerminalFactory.get<TerminalFactory.java:151> at jline.console.ConsoleReader.<init><ConsoleReader.java:140> at jline.console.ConsoleReader.<init><ConsoleReader.java::126 at net .minecraft.server.MinecraftServer.<init><MinecraftServer.java:94> at net.minecraft.server.MinecraftServer.main<MinecraftServer.java:624> at org.bukkit.craftbukkit.Main.main<Main:136> Press any key to continue . . . This error is caused by you not having Visual C++ 2008 Redistributable installed, or having the wrong version installed that matches your Java version. The version of Visual C++ 2008 Redistributable (x64 or x86) must match the version of Java you are using. If you are using Java x86 and have Visual C++ 2008 Redistributable x64 installed, it will not work. You must either use Java x64, or install Visual C++ 2008 Redistributable x86. Alternatively, add in the -nojline option which turns off jline. Error: [SEVERE] java.io.IOException: Not in GZIP format Your world may be corrupt. Try removing all plugins and mod first. If you still get this error, try running your worlds through MCEdit. If that fails, restore from backups. Here is a tutorial for fixing worlds, give it a try. Error: [SEVERE] Chunk (x, y) stored at (x, y) in world '<world name>' You have another form of world corruption. Try using chunkster or MCEdit. If that fails, restore from backups. Try this tutorial for fixing worlds. Error: Failed to bind to port Stop your minecraft server and make sure you have no instances running. Make sure you have your server-ip= blank (in server.properties). If that fails, reboot. Error: Friends are unable to connect? Check if your port is open with http://canyouseeme.org/ If it isn't, you need to check your firewall (either router, or on the server itself, or both). Make sure you have your server-ip= (Yes, no IP listed at all in the server.properties. Leave the part after the = blank). Test your DNS if you are trying to connect with a name, not IP (ex: test.server.org, not 22.214.171.124). A simple test is to ping your DNS name (ex: ping test.server.org). If you do not see a IP address being resolved (even if it doesn't respond to a ping) you have a DNS problem. Error: Friends are now unable to connect... but could X time ago! Your local IP address may have changed. Check that in Windows by running ipconfig, and finding your IPv4 address. On most networks it will start with 192.168. You can also (on any platform) log in to your router's interface and find the DHCP section or clients table. You should be able to find your computer in that table, and also your IP. If it's different from the one your port is already forwarded to, change it. Make sure you have your server-ip= blank (in server.properties). Alternatively, your external IP may have changed. Simply go to www.whatismyip.org or again to your router's interface and give your friends the new one. To avoid this from ever happening, www.dyndns.com offers free hostnames and a client you can install on your computer which will always keep the name pointing to you. Test your DNS if you are trying to connect with a name, not IP (ex: test.server.org, not 126.96.36.199). A simple test is to ping your DNS name (ex: ping test.server.org). If you do not see a IP address being resolved (even if it doesn't respond to a ping) you have a DNS problem. Error: After downloading the new CB, my server closes immediately after opening and says file or directory not found (Could not access jarfile craftbukkit.jar). Not all versions of CraftBukkit are named craftbukkit-0.0.1-SNAPSHOT.jar anymore. You probably entered that name when making the startup script and may not even remember. Either edit your startup script to match the new name of the CB Jarfile, or just rename the CB Jarfile to craftbukkit-0.0.1-SNAPSHOT.jar. Beware if you are using Windows. Windows will hide the file extension by default, so try renaming the file to just: craftbukkit Alternatively, unhide file extensions. Error: System cannot find path specifiedwhen launching server [DETAILED] This is normally fixed by changing the location of where the CraftBukkit jar is in the bat file Most craftbukkit files come as craftbukkit-<version>-R<version>.jar, this HAS to the same in the bat file unless you changed otherwise. Examples of a bat file (With Bukkit jar named as 'craftbukkit.jar') @Echo off "C:\Program Files (x86)\Java\jre6\bin\java.exe" -Xms1024M -Xmx1024M -jar craftbukkit.jar pause Rundown: @Echo off - Hides unwated lines from CMD "C:\Program Files (x86)\Java\jre6\bin\java.exe" - your Java.exe location -Xms1024M and Xmx1024M - Amount of RAM you want to run the server on in MB -jar - Just CMD to run a .jar file craftbukkit.jar - The name which you have given your bukkit file - default is: craftbukkit-1.0.1-R1.jar pause - Leaves CMD window open to allow for commands So, if you are running Java6 (32 bit) on a 64bit machine it would look like this (with default jar location) How it would look (With default naming) on x86 or x64 machines. x86(32 Bit) @Echo off "C:\Program Files (x86)\Java\jre6\bin\java.exe" -Xms1024M -Xmx1024M -jar craftbukkit-1.2.5-R4.jar pause x64(64 Bit) @Echo off "C:\Program Files\Java\jre6\bin\java.exe" -Xms1024M -Xmx1024M -jar craftbukkit-1.2.5-R4.jar pause Error: NoSuchMethodError or ClassNotFoundException in error message. If you are seeing any of these phrases in your error, something new is most likely conflicting with something old. Search the error for a plugin name, if found, update the plugin in the error. If not found, update Java. Error: Outdated Server The client version of Minecraft you are using is newer than the server version of Minecraft you are connecting to. Downgrade your client, or try connecting to the server once they have updated. Fatal Error: ConcurrentModificationException This fatal exception is caused in CraftBukkit by a poorly written plugin. Try removing any of your recently added plugins first. If you still get this error, try removing all of your plugins and adding them back in one by one until the problem comes back. Updating the plugin to a newer version may help. Error: [SEVERE] java.net.SocketException: Socket Closed Example Error: Code: 2011-11-30 00:39:34 [SEVERE] java.net.SocketException: Socket closed 2011-11-30 00:39:34 [INFO] Connection reset 2011-11-30 00:39:34 [SEVERE] at java.net.SocketOutputStream.socketWrite(Unknown Source) 2011-11-30 00:39:34 [SEVERE] at java.net.SocketOutputStream.write(Unknown Source) 2011-11-30 00:39:34 [SEVERE] at java.io.BufferedOutputStream.flushBuffer(Unknown Source) 2011-11-30 00:39:34 [SEVERE] at java.io.BufferedOutputStream.flush(Unknown Source) 2011-11-30 00:39:34 [SEVERE] at java.io.DataOutputStream.flush(Unknown Source) 2011-11-30 00:39:34 [SEVERE] at net.minecraft.server.NetworkWriterThread.run(SourceFile:104) This error is harmless, it occurs when someone disconnects using the 'x' button instead of disconnecting and then quitting minecraft. Problem: How do I find my server IP? You can find the IP address of your computer by visiting this site: http://whatismyip.org/ You still want to keep the server-ip setting in your server.properties blank, however. Problem: How do I change the map seed? There is an option in your server.properties file: level-seed= Just set that whatever you want, and move/rename the current world to generate a new one. Problem: I keep getting kicked for flying. Open up your server.properties and make sure allow-flight is set to true. allow-flight=true Problem: Only OP's can place blocks near the spawn. Open bukkit.yml in your servers root and change the spawn radius from 16 to a smaller number. spawn-radius: 1 Problem: Permissions doesn't work and/or returns errors This is most likely caused by incorrect syntax in the YAML data files permissions plugins use. A good diagnostic parser can be found here. Paste your config file into the left box, and the right box will tell you where the errors can be found. Remember, YAML entries must have a colon ":" and lines must never have tabs. If this doesn't fix your problem, it may be a bug with the plugin or some other problem preventing your permissions plugin from working correctly. I get an error on the console! What's the problem? When you get an error in the console you can easily check if it's an Bukkit error or a plugin is giving errors. If an plugin gives an error you should contact the plugin developer. Example Bukkit error Code: 10:02:47 [SEVERE] java.lang.NullPointerException at net.minecraft.server.PlayerManager.flush(PlayerManager.java:34) You can see this because the second line says [SEVERE] at net.minecraft.server... This means there is an error in net.minecraft.server and that's the server software (aka Bukkit.) Example Spout error Code: 2011-11-24 16:28:42 [SEVERE] Could not pass event PLAYER_JOIN to Spout java.lang.NoSuchFieldError: k at org.getspout.spout.SpoutNetServerHandler.sendPacket(SpoutNetServerHandler.java:470) Here you can see that the error is in org.getspout.spout. You should get help from the Spout developer for a fix. (PS: This is an example. It could also say me.dadaemon.MyOwnProPlugin.) Problem: Client crashes when something happens on a server. This probably means your system cannot handle minecraft properly in multiplayer. Try and verify that this problem does indeed occur on other servers. You may need more ram, or if you haven't already, install java7 (oracle's version, not openJDK) as it has performance fixes and some optimizations over java5 and java6. Another cause of this problem is that you may have installed some client mod that is messing with the game, or minecraft has become corrupted somehow. To un-corrupt/redownload, open minecraft, and before logging in, click "options" then click "force redownload". When you log in, it will redownload minecraft. Problem: People cannot join hamachi-based server. Verify that the users have the hamachi software. They will need hamachi to connect. If you are unable to join using the address given, try running the server without hamachi, and connect with your local ip. (See how to find your local IP below) If it works with your local ip, try to port forward. Visit http://portforward.com/ if you don't know how. Error: Could not find main class This means java is out of date. Please install either java6 or java7. (Preferably sun/oracle version) Error: java.lang.UnsupportedClassVersionError This means java is out of date, or a plugin you are using uses a newer java version than you have installed. Please install either java6 or java7. (Preferably sun/oracle version) Problem: endOfStream while joining a server. endOfStream is a network error in java that occurs when either the client or server hang up on each other. It is typically a problem with the server. A common solution is to simply restart the server. Restarting periodically may also be a good idea, and there are plugins that do just that. Note: restarting is NOT the same as reloading. Reloading often glitches, especially with the new beta builds. How to find your local IP (windows only): To find your local IP, check this informative article:http://www.groovypost.com/howto/microsoft/windows-7/find-your-local-ip-address-windows-7-cmd/ (steps 1&2 only) (Also works on vista) For XP, press the windows flag key and "r" at the same time, then type "cmd.exe" in the window. Then do step 2. This list is just a start. Please include problems and known, verifiable solutions - I will add them as they come in. Requests/responses for help in this thread will be deleted. I am getting Lag! What can I do? There are multiple ways to tackle this problem. You WILL have to spend time searching and troubleshooting, so do not look for an easy fix. Most lag issues are caused by plugins. Try removing them one by one until you find the culprit. You can also use a program to check your worlds for problems. Chunkster and Minecraft Region Fixer are both good tools to use. Alternatively, use a Java profiler. @md_5 wrote up a good tutorial on a free Java profiler called VisualVM: http://forums.bukkit.org/threads/wip-analysis-of-your-server-jvm-using-visualvm.66536/ If you have read this thread, and think you're problem lies outside of what is outlined above, you probably have a plugin issue. However, read through this and ask a question on the forums if you feel your question is still unanswered. While I will not tolerate blunt rudeness in response, it is UP TO YOU to do your due diligence when searching for help. Thanks @Archelaus @pyraetos @saul100 @Perdog @tyzoid @Acrobot and everyone for the additional tips and solutions. Please keep them coming.