I’m constructing a MOD that implements

MyBlock extends net.minecraft.block.Block 

and an associated

MyTileEntity extends net.minecraft.tileentity.TileEntity

that should open

MyGuiScreen extends net.minecraft.client.gui.GuiScreen

when the Minecraft Server decides to.  The client side will ask the server to open MyGuiScreen and the Server will open it, after taking security concerns into account.

 

Currently I have MyGuiScreen opening just fine when the client decides to, like this

if (worldIn.isRemote) playerIn.openGui(MyMod.INSTANCE, MyGuiHandler.GUI_ID, worldIn, x, y, z)

 

How do I allow the server to open MyGuiScreen at the client after the server receives a request from the client to do so?

 

If you call

EntityPlayer#openGUI

on the server and your

IGuiHandler#getServerGuiElement

method returns a

Container

, FML will send a packet to the client telling it to open the same GUI (via your

IGuiHandler

).

 

If the open request needs to be sent from the client side (e.g. in response to a key press), send a custom packet to the server. The same applies if your GUI doesn't have a

Container

and you need to send the response packet manually.

 

Forge's documentation explains networking in Minecraft here. This includes the Simple Network Implementation, which you should use to send the packet.