If this helps anyone, I wrote an adapter to treat a java.util.concurrent.SubmissionPublisher as a Manifold sink: https://gist.github.com/KingMob/149e1b21674c9b027699753143878ab8 I ended up choosing to use Websockets in the end, but I did successfully use this for a few weeks. (The reason I switched is the whole http://reactive-streams.org / Java Flow design is more like a complicated, pull-based lazy sequence, while most reactive patterns, including Manifold, are more like blockable chains of dominos. I understand the stated goals of http://reactive-streams.org, I just don't think the result very stream-like)