Slot Data

The slot data structure is how minecraft represents an item and its associated data in the minecraft protocol

Packets

• 0x0F player block placement
• 0x66 window click
• 0x67 set slot
• 0x68 window items (as an array)
• 0x6B creative inventory action

Format

The structure consists of at least a short, which gives the item/block ID [1]. A value of -1 signifies that the slot is empty, and no further data follows.

For non-empty slots, at least two further fields follow. These fields are a byte (item count) and a short (damage/block metadata)

For every block ID, except -1, further data follows. First, a short gives the length of a proceeding byte array. A value of -1 signifies no further data.

The byte array (if present) contains gzipped (that is RFC 1952 rather than RFC 1950) NBT data. The format of this data is as follows:

 COMPOUND: ''
   LIST: 'ench'
     COMPOUND
       SHORT: 'id'
       SHORT: 'lvl'
     END
     COMPOUND
       ...etc
     END
 END

Each of the inner, untagged COMPOUNDs represents an enchantment, with its ID[2] and level given as child SHORT elements.