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How to make a server-side-only mod?

Alsan Ali

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Here's my mod annotation:

@Mod(modid = SomeRandomMod.MODID, version = SomeRandomMod.VERSION, serverSideOnly = true)


Even though serverSideOnly is set to true, I still get a mod rejection when trying to connect to the server. I don't want to install the mod in my client. Here are the stuff my mod does, not sure if all of them are server-side:

  • Registers some basic commands (the commands don't do anything except send the player messages)
  • I also have an instance of MinecraftServer which I use to shutdown the server (server.initiateShutdown)
  • There's a PlayerEvent.PlayerLoggedInEvent which is registered
  • A CommandEvent and ServerChatEvent which are registered as well
  • Connects to a SQLite database
  • Use the EntityPlayer class
  • Use potion effects
  • Use InventoryPlayer class
  • Use MobEffects class


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serverSideOnly just tells the client to skip loading the mod if it's installed, you need to set the acceptableRemoteVersions property to "*" as well. This tells it to accept any remote version, including none.

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Please don't PM me to ask for help. Asking your question in a public thread preserves it for people who are having the same problem in the future.

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Oh wow. I probably will never make a server-only mod, but this is actually VERY useful information!

Follow these rules when talking to me, and we'll get along fine.

1).I know Java fairly well. I don't know as much about modding. They are not the same, don't compare them.

2). I consider myself to always be learning. I make mistakes, you make mistakes. Who doesn't?

3). Insult me, and I will leave the thread. I have a real life, I don't have time to throw petty insults in a Minecraft Modding forum.


ModMCdl - Co-Founder and Director of Design for Artemis Game Studios

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Is it possible to do this in Forge itself? Like, the client doesn't need to have Forge installed, kinda like Bukkit or Spigot. It's ok though, if this isn't possible. And do you know any reliable way of getting an instance of MinecraftServer? Here's my current way of doing it:


public static void makeInstance(MinecraftServer minecraftServer) {
    	EBMCore.minecraftServer = minecraftServer;


This method is called when I do my custom command '/initialize'. So I have to do the command immediately after the server starts (every time). This is the only method I've figured out ._.

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8 minutes ago, Alsan Ali said:

Is it possible to do this in Forge itself? Like, the client doesn't need to have Forge installed, kinda like Bukkit or Spigot.


The client only needs Forge installed if the server's mods need to be installed on the client. If none of the server's mods are required on the client, a Vanilla client can join.



8 minutes ago, Alsan Ali said:

And do you know any reliable way of getting an instance of MinecraftServer? Here's my current way of doing it:


In what context?


If you have a MinecraftServer argument available, use that. If you have an object with a method that returns MinecraftServer (e.g. World#getMinecraftServer), use that.


If all else fails, you can use FMLCommonHandler#getMinecraftServerInstance.

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Please don't PM me to ask for help. Asking your question in a public thread preserves it for people who are having the same problem in the future.

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The main mod I've kept going the last few years is basically a server plug-in also (its all world gen), and never had any trouble.  My advice would be to use the acceptableRemoteVersions tag to not require any version on the client -- I wouldn't even bother with ServerSideOnly, just in case someone want to use it in single player (whether it makes much sense or not).  Assuming you don't use anything that needs client side functioning, that should be good.

Developer of Doomlike Dungeons.

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  • 1 year later...
6 minutes ago, Xaser said:

But the server will still say "[FML]: Attempting connection with missing mods [my_mod] at CLIENT" when doing so. Is this intended?

Yes. That it is telling you that it's going to attempt the connection. The mods then decide if they allow the connection even when the remote party does not have it installed.

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Thanks. Another quick question. When using the local server, my mod won't work and the console says



[14:14:05] [Client thread/INFO] [FML]: Disabling mod my_mod it is server side only.
[14:14:05] [Client thread/INFO] [FML]: Forge Mod Loader has identified 14 mods to load
[14:14:05] [Client thread/INFO] [FML]: FML has found a non-mod file my_mod.jar in your mods directory. It will now be injected into your classpath. This could severe stability issues, it should be removed if possible.


So perhaps I should set AcceptableRemoteVersions to * but not say ServerSideOnly?

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