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68 lines
2.0 KiB
Markdown
68 lines
2.0 KiB
Markdown
NIP-27
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======
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Multicasting
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------------
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`draft` `optional` `author:cameri`
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A new tag `m` meaning `multicast group` allow for events to be addressed to a
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group of clients simultaneously. Multicast in this scenario can be one-to-many
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or many-to-many.
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A relay MUST forward events containing `m` tags strictly to clients subscribed
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with a tag filter `#m` containing at least one of the values of such tags and
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refrain from forwarding such events to clients without such filter. The value
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of an `m` tag is case-sensitive.
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A client SHOULD send events containing `m` tags only to relays that explicitly
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support NIP-27. A NIP-16 supporting client MAY test for the capability by
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subscribing twice to a relay with and without the tag filter `#m` respectively
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and sending an ephemeral event with a random `m` tag of equal value.
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## Events
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Clients targeting a multicast group MAY include an `m` tag with a value set to
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an arbitrary string representing the multicast group.
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Suppose that Alice wants to multicast an event to a very special multicast group
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that covers specific topics. The multicast group is identified by the following
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string: `00000000839a8e6886ab5951d76f411475428afc90947ee320161bbf18eb6048`
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Alice would construct the following message and sends it to her favorite relay
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which happens to support multicasting:
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```json
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[
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"EVENT",
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{
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"id": "<id>",
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"pubkey": "<Alice's pubkey>",
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"created_at": 1231469640,
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"content": "Let's get the conversation started",
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"tags": [
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["m", "00000000839a8e6886ab5951d76f411475428afc90947ee320161bbf18eb6048"],
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],
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"sig": "<sig>"
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}
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]
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```
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## Subscriptions
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Clients subscribing to a multicast group MUST include an `#m` tag filter with
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an array of multicast groups as values.
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Suppose that Bob and Charlie both share Alice's interest and would like to stay
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up to date. Both would construct the following message to subscribe:
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```
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[
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"REQ",
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"<subscriptionId>",
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{
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"#m": ["00000000839a8e6886ab5951d76f411475428afc90947ee320161bbf18eb6048"]
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}
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]
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```
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