bash, /dev/net and you
found during a random goog search on Dave Smith’s Blog:
exec 3<>/dev/tcp/www.google.com/80 echo -e "GET / HTTP/1.1\n\n" >&3 cat <&3
seriously, wrap your head around that. /dev/net isn't a real device, it's a magical pseudodevice that bash intercepts and opens a socket as requested.