Building a Bitcoin IPN. Need unique identifier

Question

I am building a Bitcoin IPN to poll bitcoind every 5 minutes, find new payments with at least 1 confirm, and notify a server.

It looks like I am going to have to load them all up with 'listtransactions' every time and parse out new ones. Inelegant, but I don't see any other option.

So the next problem is that I need a unique identifier of payments so that I can see if it has already sent a notice. I have read that txid can change? Well, that is not a bloody ID then, is it?! How can I identify a payment? sha1(address . amount . time) ? What is the difference between 'time' and 'timereceived'? Are they static?

The best discussion I found about this is here but it doesn't look like it went anywhere;

https://bitcointalk.org/index.php?topic=3092.0

Cheers.

Answer 1

TXIDs cannot change. TXIDs are simply hashes of the transaction. It is possible for two different transactions to have the same TXID - that's called a hash collision. However, the chances of that happening are so low and I believe you will actually win prize money if you find a collision.

Answer 2

I am building a Bitcoin IPN to poll bitcoind every 5 minutes

Investivate -blocknotify, which will turn your system from pull to push. Any command given to blocknotify will be executed when a new block is encountered, and you can use this to update your internal systems with the newly confirmed data.