Preventing TCP SYN retry in netcat (for port knocking)
问题 I'm trying to write the linux client script for a simple port knocking setup. My server has iptables configured to require a certain sequence of TCP SYN's to certain ports for opening up access. I'm able to successfully knock using telnet or manually invoking netcat (Ctrl-C right after running the command), but failing to build an automated knock script. My attempt at an automated port knocking script consists simply of "nc -w 1 x.x.x.x 1234" commands, which connect to x.x.x.x port 1234 and