This is a list of some (systems providing) APIs that we can look at in order to understand what kinds of transport services applications may want from the network. They are discussed in draft-hurtig-tsvwg-transport-apis
Apache Portable Runtime, with its many socket functions and options. There was once an effort to integrate SCTP, not sure how far this is now... some people at the University of Delaware worked on this, including Jana Iyengar.
Java JDK, apparently with SCTP support, but exposing it pretty clearly it seems...