Show Note

open ssh tunnel from your local machine

For running Rails app in development, you can do this since rails s runs on port 3000.

localhost$ ssh -R 8088:localhost:3000 remote_server -N &

This creates a tunnel that binds remote TCP port 8088 to local TCP port 3000.

-R flag is for remote binding which tell the remote server to send TCP traffic on port 8088 to my machine. This is basically reverse of -L which binds the local machine’s port to remote.

8088: specifies the port on remote server. Therefore, following command on remote server will give a result assuming that I’m running a Rails app on port 3000.

remote_server$ curl localhost:8088

localhost is the host, obviously my local machine where the traffic will bind to.

:3000 is the local port you want to bind the traffic to.

-N tells ssh to not execute a remote command. Should always use this if we’re just tunneling.

& makes it run in background.

install socat if not installed on remote server

This is the definition from socat.

Socat is a command line based utility that establishes two bidirectional byte streams and transfers data
between them

For Ubuntu, remote_server$ sudo apt-get install socat will do.

run socat to relay public traffic

On remote server, expose a public port and then route the traffic to local port that’s bound to my local machine.

remote_server$ socat TCP-LISTEN:8090,fork,reuseaddr TCP-CONNECT:127.0.0.1:8088 &

TCP-LISTEN:8090,fork,reuseaddr tells socat to listen TCP on port 8090, creating a server at that port. The options are self-explanatory.

TCP-CONNECT:127.0.0.1:8088 tells socat to connect TCP to localhost at port 8088 which is bound to my machine.