I'm using an NWConnection to talk to a TCP endpoint. The connection steps are working fine and I'm able to receive some data, but not all the data I expect. I am posting to see if I misunderstand how the NWConnection is supposed to behave.
The messages I want to receive have a header and a payload. The header tells me how many bytes are in the payload. To do that I am trying to call receive twice on the connection. The first receive looks something like
connection.receive(minimumIncompleteLength: MessageHeader.PackedDataCount,
maximumLength: MessageHeader.PackedDataCount) { … }
The second receive call is very similar and tries to grab the payload. It looks something like:
let payloadLength = messageHeader.payloadLength
connection.receive(minimumIncompleteLength: payloadLength,
maximumLength: payloadLength) { … }
The first message sent by the server has the bytes [0x0F, 0x00, 0x01, 0x02].
The first three bytes are the header and indicate that the message type is 0x0F, of length 1 byte (0x0001) and the payload is one byte, 0x02.
When I run my code, the first call to receive works fine. I get three of the four bytes sent by the server. The second call to receive, however, never returns the one remaining byte (the callback is never invoked).
If I change the first receive call to ask for 1024 as a maximum length then I can see all 4 bytes from the server in the response so I know all the data I want was sent.
But I can't receive it in two subsequent calls to the connection.
Do I misunderstand the way that receive is supposed to behave? If the server sends four bytes, do I have to read them all in one call to receive?
