As I imagine you discovered, port scanning can be brutally slow, yet, in most cases, is not processing intensive. Thus, we can use threading to drastically improve our speed. There are thousands of possible ports. If it is taking 5-15 seconds per port to scan, then you might have a long wait ahead of you without the use of threading.
Oct 21, 2015 How to Create SSH Tunneling or Port Forwarding in Linux Sep 26, 2018 SSH port forwarding - Example, command, server config Frequently, the port is tunneled to an SSH port on an internal machine. In OpenSSH, local port forwarding is configured using the -L option: ssh -L 80:intra.example.com:80 gw.example.com. This example opens a connection to the gw.example.com jump server, and forwards any connection to port 80 on the local machine to port 80 on intra.example.com. How to Set Up Port Forwarding - Lifewire
How to configure SSH port forwarding (Tunneling) in Linux
How to Set up Port Forwarding with iptables | Ivo Berger I'll assume a scenario where you want to access an internal server with an internal IP 10.0.0.1 on port 80 through a server with an external IP 32.0.0.1 on port 8080 using TCP. First we need to allow forwarding on the kernel level as this is usually disabled by default.
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Oct 21, 2015 How to Create SSH Tunneling or Port Forwarding in Linux Sep 26, 2018 SSH port forwarding - Example, command, server config Frequently, the port is tunneled to an SSH port on an internal machine. In OpenSSH, local port forwarding is configured using the -L option: ssh -L 80:intra.example.com:80 gw.example.com. This example opens a connection to the gw.example.com jump server, and forwards any connection to port 80 on the local machine to port 80 on intra.example.com. How to Set Up Port Forwarding - Lifewire