You've already forked specification
Andrew Groot
46 lines
2.7 KiB
Markdown
46 lines
2.7 KiB
Markdown
<div class="cwikmeta">{
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"title":"XVERSION",
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"related":["/protocol/network/messages","/protocol/network/messages/xupdate","/protocol/network/messages/xverack"]
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}</div>
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# Handshake Extension: XVersion (“xversion”)
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This message notifies a peer about extended protocol parameters. This message MAY be sent during connection initialization. If sent, it MUST be sent immediately subsequent to the receipt of the [`verack`](/protocol/network/messages/verack) message, and before other non-initialization messages are sent.
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## Message Format
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| Field | Length | Format | Description |
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|--|--|--|--|
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| number of values | variable | [variable length integer](/protocol/formats/variable-length-integer) | The number of values being sent. |
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| values | variable | `number_of_values` * [xversion values](#xversion-value-format) | The list of values to communicate. |
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### XVersion Value Format
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| Field | Length | Format | Description |
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|--|--|--|--|
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| field | variable | [variable length integer](/protocol/formats/variable-length-integer) | Indicates the field type of the value to follow. See [XVersion Fields](#xversion-fields). |
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| size of value | variable | [variable length integer](/protocol/formats/variable-length-integer) | The size of the value to follow. |
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| value | `size_of_value` bytes | bytes | The value for the preceding field type (`key`). The format of the value is defined by the `field`, but must be the specified number of bytes. |
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#### XVersion Fields
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XVersion field identifiers are 32 bits and split into a 16 bit prefix and 16 bit suffix. Each development group is assigned a prefix so that new identifiers do not accidentally conflict. Once a field identifier is created by group A, it should be used by other software both to receive that information from A and to present that information to other software. Therefore, group A **MUST NOT** change the syntax or semantics of a field once defined. To change a field, create a new identifier and deprecate (by no longer using the original identifier).
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#### Prefix and Suffix Assignments
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##### Prefix Assignments
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| Group | Value |
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|-------------------------|-------|
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| Reserved for versioning | 0 |
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| Bitcoin Cash Node | 1 |
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| Bitcoin Unlimited | 2 |
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See [xversionkeys.dat](https://github.com/BitcoinUnlimited/BitcoinUnlimited/blob/bucash1.7.0.0/src/xversionkeys.dat) for the most up-to-date field definitions defined by the BitcoinUnlimited full node.
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Note that:
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* *u64c* refers to a [variable length integer](/protocol/formats/variable-length-integer).
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* *Changeable* fields MAY be changed during the course of a connection via the [`xupdate`](/protocol/network/messages/xupdate) message.
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### Support
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Supported by: **Bitcoin Unlimited**
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