This netcat just opens up an OCaml shell
In DamCTF, I saw that the solution to one of the challenges was to execute commands from inside of ruby programming language.
Here, I used Sys.command "ls";; to get the ls command output.
Then, I saw a folder named system.
I did Sys.command "ls system";; and saw a flag file
I used cat command on flag file and got the flag.
The flag is cvctf{J41L3d_OOOO-C4mL@@}