Thank you to Martin Lucina, Pieter Hintjens, Martin Sustrik, Mike Bridgen and others for their invaluable feedback on the contents, and for suggestions on ways to improve. Thank you also to Mikko Koppanen, Martin Hurton, Alvaro Videla, Lorenzo Alberton, Ben Gray, and all of the smart people on the ZeroMQ mailing list for helping my understanding of messaging systems in general.