dash/doc/instantsend.md

## InstantSend Technical Information

InstantSend has been integrated into the Core Daemon in two ways:
* "push" notifications (ZMQ and `-instantsendnotify` cmd-line/config option);
* RPC commands.

#### ZMQ

When a "Transaction Lock" occurs the hash of the related transaction is broadcasted through ZMQ using both the `zmqpubrawtxlock` and `zmqpubhashtxlock` channels.

* `zmqpubrawtxlock`: publishes the raw transaction when locked via InstantSend
* `zmqpubhashtxlock`: publishes the transaction hash when locked via InstantSend

This mechanism has been integrated into Bitcore-Node-Dash which allows for notification to be broadcast through Insight API in one of two ways:
* WebSocket: [https://github.com/dashpay/insight-api-dash#web-socket-api](https://github.com/dashpay/insight-api-dash#web-socket-api) 
* API: [https://github.com/dashpay/insight-api-dash#instantsend-transactions](https://github.com/dashpay/insight-api-dash#instantsend-transactions) 

#### Command line option

When a wallet InstantSend transaction is successfully locked a shell command provided in this option is executed (`%s` in `<cmd>` is replaced by TxID):

```
-instantsendnotify=<cmd>
```

#### RPC

Details pertaining to an observed "Transaction Lock" can also be retrieved through RPC, it’s important however to understand the underlying mechanism.

By default, the Dash Core daemon will launch using the following constant:

```
static const int DEFAULT_INSTANTSEND_DEPTH = 5;
```

This value can be overridden by passing the following argument to the Dash Core daemon:

```
-instantsenddepth=<n>
```

The key thing to understand is that this value indicates the number of "confirmations" a successful Transaction Lock represents. When Wallet RPC commands are performed (such as `listsinceblock`) this attribute is taken into account when returning information about the transaction. The value in `confirmations` field you see through RPC is showing the number of `"Blockchain Confirmations" + "InstantSend Depth"` (assuming the funds were sent via InstantSend).

There is also a field named `bcconfirmations`. The value in this field represents the total number of `"Blockchain Confirmations"` for a given transaction without taking into account whether it was InstantSend or not.

**Examples**
* InstantSend transaction just occurred:
    * confirmations: 5
    * bcconfirmations: 0
* InstantSend transaction received one confirmation from blockchain:
    * confirmations: 6
    * bcconfirmations: 1
* non-InstantSend transaction just occurred:
    * confirmations: 0
    * bcconfirmations: 0
* non-InstantSend transaction received one confirmation from blockchain:
    * confirmations: 1
    * bcconfirmations: 1