RegisterBlockEpochNtfn is a synchronous response-streaming RPC that registers an intent for a client to be notified of blocks in the chain. The stream will return a hash and height tuple of a block for each new/stale block in the chain. It is the client's responsibility to determine whether the tuple returned is for a new or stale block in the chain. A client can also request a historical backlog of blocks from a particular point. This allows clients to be idempotent by ensuring that they do not missing processing a single block within the chain.

RegisterConfirmationsNtfn is a synchronous response-streaming RPC that registers an intent for a client to be notified once a confirmation request has reached its required number of confirmations on-chain. A confirmation request must have a valid output script. It is also possible to give a transaction ID. If the transaction ID is not set, a notification is sent once the output script confirms. If the transaction ID is also set, a notification is sent once the output script confirms in the given transaction.

RegisterSpendNtfn is a synchronous response-streaming RPC that registers an intent for a client to be notification once a spend request has been spent by a transaction that has confirmed on-chain. A client can specify whether the spend request should be for a particular outpoint or for an output script by specifying a zero outpoint.