Are parallel calls to send/recv on the same socket valid?
- Can we call send from one thread and recv from another on the same socket?
- Can we call multiple sends parallely from different threads on the same socket?
I know that a good design should avoid this, but I am not clear how these system APIs will behave. I am unable to find a good documentation also for the same.
Any pointers in the direction will be helpful.
Answer
POSIX defines send/recv as atomic operations, so assuming you're talking about POSIX send/recv then yes, you can call them simultaneously from multiple threads and things will work.
This doesn't necessarily mean that they'll be executed in parallel -- in the case of multiple sends, the second will likely block until the first completes. You probably won't notice this much, as a send completes once its put its data into the socket buffer.
If you're using SOCK_STREAM sockets, trying to do things a parallel is less likely to be useful as send/recv might send or receive only part of a message, which means things could get split up.
Blocking send/recv on SOCK_STREAM sockets only block until they send or recv at least 1 byte, so the difference between blocking and non-blocking is not useful.