[cle]

How is it a fundamental difference? Unix streams are character messages, so this is basically a superset of that functionality.

(I don't know much about Unix streams, so correct me if I'm wrong.)

[michaelmior]

Generally when a protocol is referred to as message-based it's because there's some framing around the payload. This can make it impractical as compared to a streaming protocol that just passes data back in forth. In some real-time cases, you can't tolerate the latency of waiting to bundle multiple items in a single payload but you also can't tolerate the overhead of framing many small messages.