Test NIM ports on AIX to see if are opened trhought firewall

I faced a situation where I needed test if I was able to reach a NIM server ports for the NIM service, problem is that is not so easy test all the ports, the hard way for example if you need test if would be possible resotre a machine is start the mksysb restore on the NIM and on the client, boot the server on the SMS services and see if will start normally hte installation.

As per the documentation below:

https://www.ibm.com/support/pages/nim-communication-within-firewall-environment

You can see that thare are several port/services used by the NIM, is not feasible discover only in a critical moment that you have ports blocked on the firewall.
Is not possible start all the services to test from the NIM clients.
So the easy way is.
You identify a service that respond for telnet on the localhost.
Telnet to this service, on my case I saw the port 513 up:

bash-5.0# telnet localhost 513
Trying...
Connected to loopback.
Escape character is '^]'.

Testing from the NIM clients I was able to reach the port. Now, let's suppose that you need check for example the port 3901, that is needed for the NIM work with client.
Without the specific operation that NIM and client will execute, you will not be able to do a telnet on the port.
So, on this case, I can simulate a service running on the port 3901, I just need redirect all the incoming connection on port 3901 on a port of other services already running.
Be aware, on my case I just testing the TCP connection.

To test:

ssh -g -L 3901:localhost:513 localhost

*-g : this option that will make the gateway option for ssh works, if you not put the g option, you will be unable to reach the port 3901.
*-L : this option is for the local forwarding, is forwarding all the incoming connections on the port 3901 to the port 513, remember, I already have a service running on the port 513, redirecting all from the port 3901 to this port help me to use telnet from a remote host to the nim to test if the port is opened.