What about the application programming interfaces (APIs) you expose for other applications to use to communicate with your application? What about the APIs you consume in your application? How well do they work with IPv6?
Today it seems that every application or service needs to have some type of API for other apps to use. We live in a time of mashups, where applications are frequently built by pulling data from multiple sources, using APIs of some sort. If your application lives “in the cloud,” where other applications may connect to it across the public Internet, you will have certain APIs publicly exposed to which apps connect. If your application resides on an on-premises server on an internal network, it may allow connections across that local network. Even an application installed on a single machine may expose certain APIs that allow connections from other apps running on that same machine. In all of these cases, your app may also be connecting to APIs exposed by other services and systems.
Some of these APIs may be simple web connections where information is exchanged using a data format like JSON or XML. Others may be exposed ports that allow connections using an industry-standard protocol such as the Session Initiation Protocol (SIP) or the eXtensible Messaging and Presence Protocol (XMPP, formerly known as the Jabber protocol). Still other APIs may use custom proprietary protocols.
The questions you have to answer are ...