Payment processor

[Markley]

What software exists to function as a bitcoin payment processor? for example on the gambling sites, is there a standard technology they are using?

[hexafraction]

For simpler/smaller tasks there are APIs such as blockchain.info's merchant API. Otherwise, it is possible to build a highly customized backend based on BitcoinJ (using Java, Kotlin, or some other JVM language) or another library, or by communicating with a bitcoind RPC port where appropriate. I personally tend to have gone the first two routes depending on what I was doing each time.