Expose NAT server

Allow external connection to a server under a private network

Test the server

One of the best options is to use a SSH jump host server. For example, you can use serveo.net to test.

In your proxy server, run:

/usr/bin/ssh -R 35854:localhost:3128 serveo.net

In your client, run:

export http_proxy="http://USER:[e-mail]:35854"
export https_proxy="http://USER:[e-mail]:35854"
export ftp_proxy="http://USER:[e-mail]:35854"
export no_proxy="localhost,127.0.0.1,::1"
curl http://www.google.com

Setup serveo.net as a service

Make sure systemd is installed:

apt update
apt install systemd

Create the service file:

nano /etc/systemd/system/serveo-proxy.service

With the following content:

[Unit]
Description=Serveo proxy tunnel
After=network-online.target

[Service]
User=root
ExecStart=/usr/bin/ssh -R 35854:localhost:3128 serveo.net
RestartSec=3
Restart=always

[Install]
WantedBy=multi-user.target

Start and enable the service:

sudo systemctl daemon-reload
sudo systemctl enable serveo-proxy.service
sudo systemctl start serveo-proxy.service