network connection over sf (client side)
|sfnc||host port transmit-device receive-device|
sfncd(1)) to connect to the specified host and port.It reads bytes from the standard input and transmits them across transmit-device. It receives bytes from receive-device and sends them to the standard output.
sf(1) session, which contains two nested sf(1) connections (first host, then port), and then the actual body read from the standard input. The server transmits in one sf(1) session, which begins once the host and port has been received, and it contains the response.