So i'm trying to create a chest but i'm keep getting this error.

A mod tried to open a gui on the server without being a NetworkMod

 

 

Main file

	public void load(FMLInitializationEvent event) {
      ModLoader.registerContainerID(this, 30);	  
     Block crest = new crest(1999, Material.wood).setUnlocalizedName("Crest"); 
	GameRegistry.registerBlock(crest, "crest");
	LanguageRegistry.addName(crest, "Chest");		
	GameRegistry.addRecipe(new ItemStack(crest, 1), new Object [] {
		"012", "345", "678", 
		Character.valueOf('0'), new ItemStack(Block.stone, 1), 
		Character.valueOf('1'), new ItemStack(Block.stone, 1), 
		Character.valueOf('2'), new ItemStack(Block.stone, 1),
		Character.valueOf('3'), new ItemStack(Block.stone, 1), 
		Character.valueOf('4'), new ItemStack(Block.stone, 1), 
		Character.valueOf('5'), new ItemStack(Block.stone, 1), 
		Character.valueOf('6'), new ItemStack(Block.stone, 1), 
		Character.valueOf('7'), new ItemStack(Block.stone, 1), 
		Character.valueOf('8'), new ItemStack(Block.stone, 1)
	});	
}

 

GUI

@SideOnly(Side.CLIENT)
public class Guicrest extends GuiContainer{

public Guicrest(InventoryPlayer inventory, int x, int y, int z) {
	super(new ContainerCrest());
}

protected void drawContainerForegroundLayer(int par1, int par2) {
	this.fontRenderer.drawString("Crest", 0, 0, 4210752);
	this.fontRenderer.drawString("Inventory", 0, 0, 4210752);
}


//declare your variables
private static final ResourceLocation field_110410_t = new ResourceLocation("compitem:textures/gui/container/generic_54.png");


protected void drawGuiContainerBackgroundLayer(float f, int i, int j) {
	GL11.glColor4f(1.0F, 1.0F, 1.0F, 1.0F);
	this.mc.renderEngine.func_110577_a(field_110410_t);

	this.xSize = 212;
	this.ySize = 222;
}
}

 

block file

	@SideOnly(Side.CLIENT)
public void registerIcons(IconRegister par1IconRegister){
	 this.blockIcon = par1IconRegister.registerIcon("stone.texturePath");
}

@Override
public boolean onBlockActivated(World world, int x, int y, int z, EntityPlayer player, int i, float a, float b, float c) {
	if(!world.isRemote){
		FMLNetworkHandler.openGui(player, new ContainerCrest(), 30, world, x, y, z);
	}else{
		ModLoader.openGUI((EntityPlayerSP) player, new Guicrest(player.inventory, x, y, z));
	}

	return true;
}

public TileEntity createNewTileEntity(World par1World) {
	return new TileEntitycrest();

}

 

I'm a beginner in coding and trying to learn how to create a mod. I have been coding now for a few days and this is just a error that i could not fix.

I don't have a GuiHandler. Also To what should i change the modloader thingy then? To what do i need to add what ?

 

I just started a few days ago with coding i don't know everything yet.