FRP reverse SSH through an outbound HTTP proxy
==============================================

On the Ubuntu private server, download through its HTTP proxy:
  export HTTPS_PROXY=http://proxy.company.local:3128
  curl -fsSLO https://filesv.vnstech.cloud/install-frpc-ubuntu.sh
  chmod +x install-frpc-ubuntu.sh

Install frpc:
  sudo ./install-frpc-ubuntu.sh \
    --proxy-url http://proxy.company.local:3128 \
    --token 'TOKEN_FROM_PUBLIC_SERVER'

The HTTP proxy must allow CONNECT to:
  103.56.161.160:7000

From an authorized external machine, connect to the private server:
  ssh -p 60022 PRIVATE_USER@103.56.161.160

Useful commands on the private server:
  systemctl status frpc
  journalctl -u frpc -f

The public frps service only allows reverse port 60022.
Use SSH keys and restrict public access to port 60022 with a firewall allowlist.