recvmsg_nonblock

        # BasicSocket.recvmsg_nonblock

(from ruby core)
---
    basicsocket.recvmsg_nonblock(maxdatalen=nil, flags=0, maxcontrollen=nil, opts={}) => [data, sender_addrinfo, rflags, *controls]

---

recvmsg receives a message using recvmsg(2) system call in non-blocking
manner.

It is similar to BasicSocket#recvmsg but non-blocking flag is set before
the system call and it doesn't retry the system call.

By specifying a keyword argument *exception* to `false`, you can
indicate that recvmsg_nonblock should not raise an IO::WaitReadable
exception, but return the symbol `:wait_readable` instead.