I have a question, it seems like you cant give a player any motion in this context, it works perfectly with a pig or something like that, but a player doen't want to fly away, thats weird

 

@Override
public void onLeftClick(World world, ItemStack stack, EntityLivingBase player) {
	NBTTagCompound nbt = stack.getTagCompound();
	if(!world.isRemote){
		Entity entity = null;
		if(nbt.getString("EntityID") != ""){
			WorldServer server = (WorldServer) world;
			entity = server.getEntityFromUuid(UUID.fromString(nbt.getString("EntityID")));
		}
		if(nbt.getBoolean("SomethingTaken")){
			if(entity != null){
				if(entity instanceof EntityNotFallingBlock){
					EntityBlock entityBlock = new EntityBlock(world, player, ((EntityNotFallingBlock) entity).getBlock());
					entityBlock.tileEntityData = ((EntityNotFallingBlock) entity).tileEntityData;
					entityBlock.posX = entity.posX;
					entityBlock.posY = entity.posY;
					entityBlock.posZ = entity.posZ;
					world.spawnEntityInWorld(entityBlock);
					stack.setTagCompound(new NBTTagCompound());
					entity.setDead();
				}else{
					stack.setTagCompound(new NBTTagCompound());
					float f = 2;
					if(entity instanceof EntityPlayer){
						double motionX = (double)(-MathHelper.sin(player.rotationYaw / 180.0F * (float)Math.PI) * MathHelper.cos(player.rotationPitch / 180.0F * (float)Math.PI) * f);
						double motionZ = (double)(MathHelper.cos(player.rotationYaw / 180.0F * (float)Math.PI) * MathHelper.cos(player.rotationPitch / 180.0F * (float)Math.PI) * f);
						double motionY = (double)(-MathHelper.sin((player.rotationPitch / 180.0F * (float)Math.PI) * f));
						MoreMinecraft.network.sendTo(new MessageToClient(1, motionX, motionY, motionZ), (EntityPlayerMP) player);
					}else{
						entity.motionX = (double)(-MathHelper.sin(player.rotationYaw / 180.0F * (float)Math.PI) * MathHelper.cos(player.rotationPitch / 180.0F * (float)Math.PI) * f);
						entity.motionZ = (double)(MathHelper.cos(player.rotationYaw / 180.0F * (float)Math.PI) * MathHelper.cos(player.rotationPitch / 180.0F * (float)Math.PI) * f);
						entity.motionY = (double)(-MathHelper.sin((player.rotationPitch / 180.0F * (float)Math.PI) * f));
					}
				}
			}
		}
	}
}

 

And yes the method gets called

dont message the client about its motion. set it on the server, just like u have done for everythign else then player

Well I did, but it doesn't work

The player just dropps to ground, as I remember correctly, the motion handling is done by client?

Hmm I might be wrong there.

If u are able to find out where the player gets knockbacked (from attacks etc) u will find ur solution for sure

Well I didn't find the solution so far, but what I also found out is, that you can't giva a player a potion effect only on server side, so you can only make the player move if the client agrees with that, thats why there can be a NoKnockBack hack, because the client doen't react on the motion change, but that doen't help me, my idea was, to give the player an Item, which makes him move, but that won't work if he has full inventory, so I don't have any idea what to do

Well, I think thats bad code of Mojang, because in a game like CSGO, everything has to be handled by server, otherways player would start hacking, but well, its not the time to dicuss why minecraft is coded bad. Anyone has an idea how to make the player knockback?

Minecraft, and CS:GO in that matter, get input on the client. If you send that to the server, move the player in there, and then notify the player, you get some stuttering on the client. To solve this, they let the client make predictions about the player movement, and then every once in a while the server notifys the client and changes his position the the correct one if the client is wrong. This way, player movement is so smooth, even when there is server lag. So, always do movement on both the client and server.

Here a code from old versions of my mod.. see if this works for you. Used on leftClickEntity of an item...

 

 

    
    public boolean onLeftClickEntity(ItemStack stack, EntityPlayer player, Entity entity) 
    {
    	if(entity instanceof EntityLivingBase)
    		((EntityLivingBase) entity).knockBack(player, 30, player.posX - entity.posX, player.posZ - entity.posZ);
    	
    	return false;
    }