What socket send/recv operations can run concurren

Question

I am aware that one can run async_send and async_receive operations concurrently on TCP and UDP sockets. But what is the expected behavior in these situations:

1. calling two async_send operations concurrently on an UDP socket.
2. calling two async_receive operations concurrently on an UDP socket.
3. calling two async_send operations concurrently on a TCP socket.
4. calling two async_receive operations concurrently on a TCP socket.

I'm mainly interested in the first case; since UDP doesn't necessarily preserve the order of sent packets, I don't care much if they are sent in order different from the one async_send was invoked.

Answer 1

The same thing happens as would happen without Boost ASIO:

calling two async_send operations concurrently on an UDP socket.

Both datagrams will be sent.

calling two async_receive operations concurrently on an UDP socket.

It is arbitrary which operation will receive the next datagram, but both operations will behave normally.

calling two async_send operations concurrently on a TCP socket.

The data may interleave unpredictably.

calling two async_receive operations concurrently on a TCP socket.

The data may interleave unpredictably.