so there is a set of applications that position itself as a distributed cluster O/S called DCOS.
It has an MPI and spark running on top of it.
I am a developer and I have a set of distributed services running connected via socket or ZeroMQ communication system.
How can I port my existing services to DCOS?
Meaning use it's communication facilities instead of sockets/zmq.
Is there any API \ Docs on how not to run it but develop for it?
There are a number of ways to get your application to run on DCOS (and/or Mesos).
First for legacy applications you can use the marathon framework which you can view as kind of the init system of DCOS/Mesos. If you need more elaborate applications and want to really program against the apis you would write a mesos framework: see the framework development guide for more details. For deeper integration of your framework into DCOS as for example using the package repository/ command line install option check out/contact mesosphere for more details.
Hope this helps! Joerg