ServerSendChatTest.java

import net.minecraft.util.ChatComponentText;
import net.minecraftforge.common.MinecraftForge;
import net.minecraftforge.event.ServerSendChatEvent;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.common.event.FMLPreInitializationEvent;
import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;

@Mod(modid = "ServerSendChatTest", version = "1.0")
public class ServerSendChatTest {

	@Mod.EventHandler
	public void preInit(FMLPreInitializationEvent event) {
		MinecraftForge.EVENT_BUS.register(this);
	}
	
	@SubscribeEvent
	public void serverSendChat(ServerSendChatEvent event) {
		event.setMessage(new ChatComponentText("[Debug]").appendSibling(event.getMessage()));
	}
	
}