Network framework only receiving first chunk of data

Question

pwiseman OP

Created Aug ’22

Replies 2

Boosts 1

Participants 2

Hey

I've run into an issue using network framework in that I'm only receiving the first chunk of data. I really can't tell if it's how I'm using the Network.framework bits on the client side, or if it's an issue with the server side (I'm using Vapor).

I put together a basic example project that hopefully demonstates the issue. If you run the server target and then the client target for me I receive 174 bytes in the first receive, receive is then called again but nothing happens after that I'm at a bit of a loss as to why

https://github.com/GP89/TestStaticServer

Thanks!

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Answer 1

pwiseman OP

Aug ’22

Ok I realised what my problem was. It was casting the data to (char*). I did this as that's the type I needed the data in. But strlen and other things will stop at the first null byte so it seemed like I was only receiving a little bit of the data. It will also read passed the end of the context when casting the data bytes to char*, then you get that data again on the next receive which is also an issue.

I'm still confused however why is_complete isn't coming back as true, so it sits on the next receive forever

0

Answer 2

DTS Engineer OP

Apple

Aug ’22

I'm still confused however why is_complete isn't coming back as true, so it sits on the next receive forever

If you’re using a stream-oriented protocol such as TCP, there are no protocol-level message boundaries [1]. If the sender sends you 2 chunks of 2048 bytes, you might receive:

2 chunks of 2048 bytes
1 chunk of 4096 bytes
4096 chunks of 1 byte
2 chunks of 1450 bytes followed by 1 chunk of 1196 bytes
Or any other combination

There’s no way that is_complete can be set at message boundaries because message boundaries aren’t reflected in the underlying protocol. With TCP, you’ll only see is_complete set at the end of the stream.

If you need message boundaries on top of TCP, add a framing protocol. The easiest to apply here is WebSocket, which has built-in support in Network framework.

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[1] Technically TLS-over-TCP adds message boundaries but that’s not reflected in most TLS APIs, including Network framework, where the goal is for TLS-over-TCP to act as much like TCP as possible.

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