Broadcast | nostrbase docs

Send and receive

const room = db.channel("editor", { broadcast: { self: true } });

room
  .on("broadcast", { event: "cursor" }, ({ payload, pubkey, sessionId }) => {
    console.log(payload, pubkey, sessionId);
  })
  .subscribe();

const { data, error, meta } = await room.send({
  type: "broadcast",
  event: "cursor",
  payload: { x: 120, y: 80 },
});

Use { event: "*" } to receive all broadcast event names.
Self delivery is off by default. Other sessions with the same signing key still receive messages.
A channel can subscribe and send without receive handlers.
A listener needs no signer. Sending requires an active signer.
data contains a write receipt. meta.relays records relay acknowledgements. The client’s minWriteAcks applies.
Payloads must contain JSON values. Duplicate events are ignored during their lifetime.

Delivery and privacy

Broadcast payloads and Presence state are public. Signing proves the author; it does not limit access.
Relays need not retain ephemeral events. The SDK does not put them in its event cache or offline write queue.
Relay acknowledgement proves acceptance, not delivery to every subscriber.
Presence is approximate. Disconnects, clock differences, dropped messages, or relay policies can delay joins and leaves.
Relays must accept and deliver kind 20078 and the channel tags. This is a nostrbase wire format, not a general Presence standard.
Negentropy recovers stored record events. It cannot recover ephemeral Broadcast or Presence history.