TCP Port Scanner in Bash

“I just had this quick idea to write a tcp port scanner in bash. Bash supports the special /dev/tcp/host/port file that you can read/write. Writing to this special file makes bash open a tcp connection to host:port. If writing to the port succeeds, the port is open, else the port is closed…”

http://www.catonmat.net/blog/tcp-port-scanner-in-bash/