bobbae · January 27, 2024 02:36 · Jan 27, 2024
diff --git a/ngrok_tunnel_two_commands.md b/ngrok_tunnel_two_commands.md
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+If you have a web service on your laptop that you want to expose
+to the internet but you are located behind a firewall, you can 
+use the following two commands to overcome the limitations.
+
+This is not exactly equivalent but similar to ngrok.
+
+https://ngrok.com/
+
+You need a machine on Internet that has publicly accessible IP address.
+You can use a Google Cloud free tier virtual machine.
+
+https://cloud.google.com/free/docs/free-cloud-features#compute
+
+Enable port 443 for https access on the virtual machine.
+Write down your virtual machine external IP address.  
+We will refer to it as A.A.A.A
+
+In reality A.A.A.A would be something like 123.45.67.89
+
+Install caddy on the virtual machine.
+https://caddyserver.com/docs/install
+
+SSH into the virtual machine and run step 1.
+
+```
+caddy reverse-proxy --from A.A.A.A.sslip.io -to localhost:BBBB
+```
+
+BBBB would a port number, like 9999 or 8888. You can use any number
+above 1000 that is not being used. This is the port where you will 
+be running a remote ssh tunnel port on the virtual machine.
+
+Appending sslip.io to the IP address like A.A.A.A (for example,
+123.45.67.89.sslip.io) allows you to use an IP address as
+a domain address.  sslip.io resolves IP address to itself.
+
+https://sslip.io/
+
+Now, to expose your local web server running on a laptop for example.
+
+Step 2:
+
+```
+ssh -f -N -t -R BBBB:localhost:CCCC A.A.A.A.sslip.io
+```
+
+BBBB is the port you used with the caddy command in step 1.
+That is the port on remote machine, the virtual machine in the cloud,
+that will be forwarded to the local machine port CCCC.
+
+When a user who is located somewhere in Internet uses a browser to
+connect to https://A.A.A.A.slip.io, the caddy server will obtain
+TLS certificate from LetsEncrypt automatically and terminate TLS
+and forward the request to port BBBB on the virtual machine, which
+will be tunnelled to the port CCCC on the laptop via reverse
+ssh tunnel.
+
+All of this is done securely.  Even if your local web service
+is not using TLS, the ssh is secure, and caddy will terminate TLS,
+effectively making your local server https server.
+This allows you to expose your local http server to the internet
+with minimum fuss.
+
+
+@bobbae
+Comment
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