How to check more than 1 byte is ready to be read from the windows socket?

Question

I was trying through looping around ioctlselect or recv, which is consuming time. Somebody suggested to use select. select is very fast. But problem is i should receive only after more than one byte is ready to be received. select is ready if one byte is also readable from the socket. Are there any alternatives?

Answer 1

Use select, and put the socket in non-blocking mode. (See fcntl, it can do this for you.) Then, simply recv into a large buffer. If there is less data available, you'll get a short recv, and recv will return to you the number of bytes it read. If nothing is available, recv will fail, and errno will be EWOULDBLOCK or EAGAIN (check for both).

recv can fail with EAGAIN/EWOULDBLOCK even if select says data is available.

It is more efficient and easier to read as much as available, and then buffer in your code as needed.

Edit: oops, you're on Windows. Same idea, except you'll need to check Winsock's error codes, not errno, and ioctlsocket can put the socket in non-blocking mode. (I'm not sure if Windows has fcntl or not.)