How CFReadStreamRead distinguishes packets when reading?

Question

I feel I'm missing some fundamental info, however, the problem I'm facing is I'm getting one data packet that consists of two merged other packets. Server API works correct, this merge happens only when multiple writes and read occur at the same time. So, the question is if a server performs several writes via socket, who is responsible for distinguishing where a packet starts, ends and where second packet starts? Me or CFReadStreamRead?

Currently, I'm using AsyncSocket that is a wrapper around CFNetwork but IMHO the problem is somehow related to CFReadStreamRead itself: sometimes it reads two packets as one, instead of reading them separately. I was unable to find relative examples and info about how the flow goes when multiple writes and reads occur at the same time, and do I need explicitly do something to grab the packet or do I need manually to split those packets from coming data stream? Though CFReadStreamRead already does that but maybe I'm missing smth.

Answer 1

It's not clear what you mean here by "packets" and I suspect you're using the term very loosely. The place that packet (i.e. IP packet) boundaries are determined is at the network layer, which is well below any of the things you're talking about.

At the layer you're talking about, all writes are going to be joined together. Bytes are bytes. A single write does not in any way suggest a single read. Multiple writes may map to a single read or vice versa. It is up to the protocol to indicate where boundaries are between things the protocol thinks of as separate messages. In the situation you're describing, that means this is an issue between you and your server.