S.transportA transport is used to send and receive bytes and file descriptors. Typically this will just call the usual Unix sendmsg and recvmsg functions, but other transports are possible.
send data fds transmits the bytes of data and the file descriptors in fds.
recv buffer reads incoming data from the remote peer. The data is read into buffer and the method returns the number of bytes read and the list of attached file descriptors.
Shut down the sending side of the connection. This will cause the peer to read end-of-file.
up is true until the transport has sent or received an end-of-file (indicating that the connection is being shut down). This can be accessed via Proxy.transport_up.