sendmsg

sendmsg sends a message using sendmsg(2) system call in blocking manner.

mesg is a string to send.

flags is bitwise OR of MSG_* constants such as Socket::MSG_OOB.

dest_sockaddr is a destination socket address for connection-less socket. It should be a sockaddr such as a result of Socket.sockaddr_in. An Addrinfo object can be used too.

controls is a list of ancillary data. The element of controls should be Socket::AncillaryData or 3-elements array. The 3-element array should contains cmsg_level, cmsg_type and data.

The return value, numbytes_sent is an integer which is the number of bytes sent.

sendmsg can be used to implement send_io as follows:

# use Socket::AncillaryData.
ancdata = Socket::AncillaryData.int(:UNIX, :SOCKET, :RIGHTS, io.fileno)
sock.sendmsg("a", 0, nil, ancdata)

# use 3-element array.
ancdata = [:SOCKET, :RIGHTS, [io.fileno].pack("i!")]
sock.sendmsg("\0", 0, nil, ancdata)