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Andrew Groot
fed06d280a
Expanded upon some existing pages and populated some pages that were linked to despite not existing.
43 lines
2.2 KiB
Markdown
43 lines
2.2 KiB
Markdown
<div class="cwikmeta">{
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"title":"INV",
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"related":["/protocol","/protocol/network/messages/getdata.md","/protocol/network/messages/filterload.md","/protocol/network/messages/filterclear.md"]
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}</div>
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# Announcement: Inventory ("inv")
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Notifies peers about the existence of some information (block or transaction).
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Based on selected services in the [version](/protocol/network/messages/version) message, inventory messages may not be sent.
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If a bloom filter has been sent to this node via [filterload](/protocol/network/messages/filterload), a transaction inventory will only be sent for transactions that match the bloom filter.
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## Message Format
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| Field | Length | Format | Description |
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|--|--|--|--|
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| inventory count | variable | [variable length integer](/protocol/formats/variable-length-integer) | The number of inventory items in this message. |
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| inventory items | `inventory_count` * 36 bytes | `inventory_count` [inventory items](#inventory-item-format) | The set of inventory items being transmitted. |
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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](/protocol/network/messages/headers) messages in place of inventory messages when a block arrives. This behavior can be requested using the [sendheaders](/protocol/network/messages/sendheaders) message.
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#### Inventory Item Format
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| Field | Length | Format | Description |
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|--|--|--|--|
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| type | 4 bytes | [inventory type](#inventory-types)<sup>[(LE)](/protocol/misc/endian/little)</sup> | Indicates what the following hash represents. |
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| item hash | 32 bytes | bytes<sup>[(LE)](/protocol/misc/endian/little)</sup> | The [hash](/protocol/blockchain/hash) that identifies the item. |
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#### Inventory Types
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The type of the object that is available.
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| Type | Value|
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|------|------|
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| 1 | Transaction |
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| 2 | Block |
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| 3 | Filtered Block (partial block with merkle proof)
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| 4 | Compact block
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| 5 | Xthin block (Bitcoin Unlimited)
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| 6 | Graphene Block (Bitcoin Unlimited)
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Implementations: [C++](https://github.com/BitcoinUnlimited/BitcoinUnlimited/blob/eb264e627e231f7219e60eef41b4e37cc52d6d9d/src/protocol.h#L477)
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