Question

From what i’ve read around about winsock, recv has a tendency to not receive all the data from a sender in a single call. When people say this do they mean, for example, i send 300 bytes from a client and i call recv on the server, it’s possible that it could only receive 200 some bytes on it’s first call and the buffer will be filled with those 200 bytes? What happens to the last 100 bytes?

also, let’s say a buffer is too small, like 512 bytes or something and the client sends 600. will the first recv call fill the buffer to capacity, and then just drop the last 88 bytes? if i call recv again with a different buffer, will the first 88 bytes of that buffer be the rest of the data?

and thirdly, if one and two are true, and i receive a whole packet of data in separate buffers, will i have to splice them together into one buffer to start parsing my data out of it?

Answer 1

I’m assuming TCP here.

is it possible that it could only receive 200 some bytes on it’s first call and the buffer will be filled with those 200 bytes?

Yes.

What happens to the last 100 bytes?

You’ll receive them next time.

also, let’s say a buffer is too small, like 512 bytes or something and the client sends 600. will the first recv call fill the buffer to capacity, and then just drop the last 88 bytes?

No.

if i call recv again with a different buffer, will the first 88 bytes be the rest of the data?

Yes.

and thirdly, if one and two are true, and i receive a whole packet of data in separate buffers, will i have to splice them together into one buffer to start parsing my data out of it?

That’s up to you. Do you need the data in one contiguous buffer? If so, yes.