Hello,

After cancelling BlockEvent.PlaceEvent on the server side, I'd like to make sure the client knows the block hasn't been placed.

I've tried EntityPlayer.inventory.markDirty(), as well as overwriting the stack in the slot with itself, but neither updated the client. Ideally I'd like a way to do this on the server side only, without having to make changes to the client, because the mod I'm doing this in is intended to run on the server side only. If anyone has any suggestions about how to make this work, please let me know. I'll edit the post if I come up with a solution.

 

EDIT: Solved by adding the following after cancelling the event:

EntityEquipmentSlot hand = event.getHand().equals(EnumHand.MAIN_HAND) ? EntityEquipmentSlot.MAINHAND : EntityEquipmentSlot.OFFHAND;
((EntityPlayerMP) event.getPlayer()).connection.sendPacket(new SPacketEntityEquipment(event.getPlayer().getEntityId(), hand, event.getPlayer().getItemStackFromSlot(hand)));

 

Edited February 28, 20196 yr by The_Fireplace
Added solution

I've solved this in my build protection system by canceling the event on both server and client side, using the same conditions.  I can do this in my system, but it may not be feasible in yours if the data needed for the check only exists server-side.

Cancelling the event server-side ensures nobody can cheat their way past your protection (for the most part).

Cancelling the event client-side doesn't, but if used in addition to the server-side function can make your protection "prettier" by preventing the inventory desync.  If someone hacks past it, it will just prevent it server-side (again, only if you're also doing the check server-side, in an identical fashion), and give them the inventory desync, so no benefit for them aside from the very brief window of the block not existing client-side which could allow them to jump on top of it or w/e...but if they're hacking past your protection to do that, they could just as easily use simpler hacks to accomplish the same thing.

 

Once again, I only suggest this if you can do your check identically on both server and client.

16 hours ago, Laike_Endaril said:

I've solved this in my build protection system by canceling the event on both server and client side, using the same conditions.  I can do this in my system, but it may not be feasible in yours if the data needed for the check only exists server-side.

Cancelling the event server-side ensures nobody can cheat their way past your protection (for the most part).

Cancelling the event client-side doesn't, but if used in addition to the server-side function can make your protection "prettier" by preventing the inventory desync.  If someone hacks past it, it will just prevent it server-side (again, only if you're also doing the check server-side, in an identical fashion), and give them the inventory desync, so no benefit for them aside from the very brief window of the block not existing client-side which could allow them to jump on top of it or w/e...but if they're hacking past your protection to do that, they could just as easily use simpler hacks to accomplish the same thing.

 

Once again, I only suggest this if you can do your check identically on both server and client.

Yeah, the entire mod, including the data used for the check, is only on the server side.

 

Since the original post, I've also tried decreasing the stack size of the block when I cancel the event then adding the block to the inventory, but that didn't fix it either.

If you want to do it from server-side only, you'll have to see if you can find a packet that harmlessly triggers a client-side inventory sync.  I haven't looked into that, so I won't be much help.