Ability to work with sockets at a lower level for CTF tasks

[ilyash-b]

Reported by @zglozman , moved here from Wiki page

Direct netcat interface:

Ability to work with sockets at a lower level for CTF tasks; Example: say we would like to write a simple script to solve this:

~ 501 > nc 92.222.90.84 5003
2016 2767 5275 9298 9869
What is the sum of these numbers:

[ilyash-b]

Related: #526