Forward and Reverse SSH Tunnels

local_through_server.sh

# Map a local port to a target port through the remote server.

# In the example: localhost:9000 is tunneled to imgur.com:80 through example.com
# local:9000 -> exaple.com -> target:80
# you could browse to http://localhost:9000/ and browse imgur.com
# (won't see anything, because imgur has changed their stack, but the tunnel works)

ssh -L 9000:imgur.com:80 user@example.com

# Useful for: use a server as a proxy, secure a connection (ssh encrypts everything),
# jumping around a firewall or site blocker.

local_to_server.sh

# Map a local port to a port on the remote server

# In the example, we're mapping the local port 9000 to 'localhost:5432',
# but that 'localhost' is from the point of view of the server. So...
# local:9000 -> example.com:5432

ssh -L 9000:localhost:5432 user@example.com

# Useful for: expose a service on the server, like a DB, as if it were
# a local server.

remote_to_local.sh

# Map a port on the server to a local port

# On this example, we're mapping SERVER's port 9000 to 'localhost:3000',
# in this case the 'localhost' is from your local machine pot of view. So..
# example.com:9000 -> local:3000

ssh -R 9000:localhost:3000 user@example.com

# Useful for: expose a local service to the internet through the server
# name. To show your local version of a page to someone. To answer to a webhook
# from your local machine.

# NOTE: Port forwarding is disabled on ssh by default. To enable it, add:
# GatewayPorts yes
# to /etc/ssh/sshd_config

zNOTES.md

To avoid having an interactive shell

Just add -N as the first option of the command.

To learn more

https://en.wikibooks.org/wiki/OpenSSH