I don't really understand why people love so mush auto-responders, especially business people. These messages add a considerable amount of useless noise in our mailboxes. Even though I dislike those emails, it doesn't prevent companies or friends I am hosting on my servers to request them. One of those companies …
One of the features I like on my MacOS is the Support for SPARSE devices. Specifying -type SPARSE creates a disk image which expands as it is filled with data.
When executing a command on a /dev/tcp/$host/$port pseudo-device, Bash opens a TCP connection to the associated socket.