specification/protocol/network/messages/inv.md

{ "title":"INV", "related":["/protocol","/protocol/network/messages/getdata.md","/protocol/network/messages/filterload.md","/protocol/network/messages/filterclear.md"] }

Announcement: Inventory ("inv")

Notifies peers about the existence of some information (block or transaction).

Based on selected services in the version message, inventory messages may not be sent.

If a bloom filter has been sent to this node via filterload, a transaction inventory will only be sent for transactions that match the bloom filter.

Message Format

Field	Length	Format	Description
inventory count	variable	variable length integer	The number of inventory items in this message.
inventory items	inventory_count * 36 bytes	inventory_count inventory items	The set of inventory items being transmitted.

NOTE: Since a block header is a relatively small data structure, and block propagation speed is an important network metric, a peer may send headers messages in place of inventory messages when a block arrives. This behavior can be requested using the sendheaders message.

Inventory Item Format

Field	Length	Format	Description
type	4 bytes	inventory type(LE)	Indicates what the following hash represents.
item hash	32 bytes	bytes(LE)	The hash that identifies the item.

Inventory Types

The type of the object that is available.

Type	Value
1	Transaction
2	Block
3	Filtered Block (partial block with merkle proof)
4	Compact block
5	Xthin block (Bitcoin Unlimited)
6	Graphene Block (Bitcoin Unlimited)

Implementations: C++