Thank you Quinn. I did not test your sample code yet, the only difference I can think of for now is that in my case I never stopped receiving data like you're doing here. Could it be that the connection keeps calling the completion handler as long as some data is being sent (and received) and regardless of how fast the data is being received?

This is not AV data. I have to admit this is quite of a major let down, very surprised back pressure isn't part of the Network framework when a bare socket does it. I have filed a bug report already (FB9587908). Thank you very much Matt for clarifying the situation and saving me a lot of time and trouble trying to figure this out.

It does reach the other side. What I'm saying is that I can send data onto the connection much more quickly than it actually goes out on the network, which causes it to enqueue in memory (a lot). I was expecting the connection to have a small buffer and only call the completion handler of the send() method when enough data had left the buffer and went onto the network. In the current state of things, how would I know how fast the data is coming out of this internal buffer and onto the network? I would certainly need some sort of back pressure information in order to know whether it is ok to give more data to the connection. Or am I missing something?