SSH Tunneling

New to SSH? Check out my intro blog:

SSH Blog : https://hashnode.com/edit/cm7vvn7eg000209l1fr88hp1o

What is SSH Tunneling?

SSH Tunneling is like building a secure underground pipe between two computers. Imagine two laptops — one in Lahore and the other in Karachi — and we want to connect them even if they are on different networks or behind NAT/firewalls. With SSH tunneling, you can securely forward a port from one machine to another over the internet without exposing ports directly to the world.

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Why SSH Tunneling Instead of Simple SSH Port Forwarding?

Traditional SSH Port Forwarding only works if the other device is on the same network or has a public IP. But often:

• You're on different Wi-Fi or ISPs (like college vs home)

• The remote device is behind NAT or firewall

• You don’t know the public IP of the other device

That’s where SSH tunneling with third-party jump servers like serveo.net comes in — no public IP needed!

What is Serveo.net?

Serveo.net is a free reverse SSH tunneling service that acts like a middleman. It gives you a public-facing URL or port and forwards all the traffic to your local machine over SSH.

No need to install anything — just use regular ssh command!

Scenario: Haris (Client) ⬅️➡️ Dawood (Host)

We have two laptops:

• 💻 Dawood’s Laptop — the one we want to connect to (host)

• 💻 Haris’s Laptop — the one we connect from (client)

We’ll build a tunnel so Haris can SSH into Dawood’s laptop, even if they’re on completely different networks.

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🛠️ Step-by-Step Guide

🔍 Step 1: Check SSH is Enabled on Dawood’s Laptop

On Dawood's laptop, run:

sudo systemctl status ssh

If not active, start it:

sudo systemctl start ssh

You can also check if port 22 is listening:

sudo netstat -tuln | grep :22

If it doesn’t show anything, install OpenSSH:

sudo pacman -Syu openssh-server

Step 2: Know Your IP (Optional)

If you want to check your public IP manually:

ifconfig

But remember: Serveo removes the need to know public IPs altogether. This is just for knowledge.

Step 3: Create SSH Tunnel from Dawood’s Laptop to Serveo

Now, on Dawood's laptop, run this:

ssh -R 5678:localhost:22 serveo.net

Explanation:

• -R 5678:localhost:22 → This means: any connection made to serveo.net:5678 should be forwarded to localhost:22 on Dawood’s machine.

• serveo.net → The middleman server doing the tunneling.

Output should look like:

Forwarding TCP connections from serveo.net:5678

Keep this terminal open — the tunnel is now active.

What Just Happened?

We told Serveo:

“Hey, when anyone connects to port 5678 on your server, forward that request to Dawood’s port 22 on his local machine.”

So now the world has access to Dawood’s SSH (securely) — only through this tunnel.

Step 4: Connect from Haris’s Laptop

Now, on Haris’s laptop, run this:

ssh -p 5678 dawood@serveo.net

It will ask for Dawood’s Linux password (the username must match his system).

You are now connected remotely to Dawood’s machine via SSH, using the tunnel!

Now using rsync Over Tunnel (File Transfer) :

To copy files from Haris to Dawood:

rsync -avz -e "ssh -p 5678" ~/my_folder dawood@serveo.net:~/destination_folder

To pull files from Dawood to Haris:

rsync -avz -e "ssh -p 5678" dawood@serveo.net:~/remote_folder ~/local_folder

Warnings

• Tunnel breaks if Dawood closes terminal

• No authentication system on serveo.net, so only use for temporary or trusted access

• Use strong passwords or even better, set up SSH key authentication

Note: It’s not just serveo.net that you can use—there are many other services like ngrok and localXpose that help you bypass restrictions and create secure, encrypted connections. These tools are especially useful when dealing with NATs or firewalls, particularly if you need to connect across different types of network restrictions.

P.S.
If you spot any mistakes, please don't hesitate to point them out. We're all here to learn together! 😊

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Haris
FAST (NUCES)
BS Computer Science | Class of 2027

📌 Portfolio: zenvila.github.io
📌 GitHub: github.com/Zenvila
📌 LinkedIn: linkedin.com/in/haris-shahzad-7b8746291
📌 Member: COLAB (Research Lab)