Local port forwarding on a mac

Question

I need to have the mac take traffic coming into it on one port send the traffic to a different but still local port.

I.e. Traffic comes in on port 1234 and transfers to port 5900 (vnc)

This is because the router wont allow me to set up portforward where the origin and destination ports differ and I need to connect to multiple machines.

So for example in my router I have set up: port 1234 -> 192.168.0.2:1234 port 1235 -> 192.168.0.3:1235 port 1236 -> 192.168.0.4:1236

Then I need the mac to take incoming port and send it to local port 5900

Answer 1

I doubt a local SSH tunnel is the easiest solution, but to forward 1234 to 5900:

ssh -g -L 1234:localhost:5900 localhost

The -g is needed to allow remote hosts to connect to the local port 1234.

To run this in the background:

ssh -Nfg -L 1234:localhost:5900 localhost

You can include the options in your SSH config file, like LocalForward 1234 localhost:5900.

_{To test this when Screen Sharing is not running, run the built-in Python web server: python -m SimpleHTTPServer 5900, and then point a browser to http://localhost:1234}

Answer 2

This article on Port Forwarding on Mac OS X seems to have the answer.

Here is the example they provide at the end:

The following example forwards any inbound 443 traffic to PRO Server running on local host (127.0.0.1) port 4282.

sudo ipfw add 1443 forward 127.0.0.1,4282 ip from any to any 443 in