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Josh Green
46 lines
1.8 KiB
Markdown
46 lines
1.8 KiB
Markdown
# Node Handshake
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When nodes connect the issue a connection handshake in order to ensure compatibility between the two nodes.
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The handshake informs the peer of its:
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- Network Protocol Version
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- Block Height
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- Supported [Network Services](/protocol/network/messages/version#services-bitmask)
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Neither Node should send any data other than a [Version](/protocol/network/messages/version) message to the peer until it has also received a Version message.
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Once a node has received (and sent) a Version message, it may send a [Verack](/protocol/network/messages/verack) message.
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Once each Node has sent and received a Verack message, normal node operation may begin.
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## Sequence Diagram
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When a local Node initiates a connection to a remote Node, the remote Node will remain silent it receives a version message.
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```diagramLabel
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1. Local sends Version Message to Remote containing Local's Version Number.
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2. Remote sends Version Message containing Remote's Version Number.
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3. If Local's Version Number is compatible, Remote uses the lower of the two Version Numbers and sends Verack Message.
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4. If Remote's Version Number is compatible, Local uses the lower of the two Version Numbers and sends Verack Message.
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```
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```mermaid
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sequenceDiagram
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Local->>Remote: Version
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Note Right of Remote: #35;1
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Remote->>Local: Version
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Note Left of Local: #35;2
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Remote->>Local: Verack
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Note Left of Local: #35;3
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Local->>Remote: Verack
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Note Right of Remote: #35;4
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```
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The Remote Node may send a `Verack` message before it sends its own `Version` messages.
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A Node may only send a `Version` message once.
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Although a Node may connect to itself, it is usually undesired. Nodes typically check for a connection to itself by checking if the `nonce` provided by a `Version` message is a nonce it has used recently. |