Mapping a port on another one

[LonelyStar]

Hello,

I have a vServer with gentoo on it.
I am sending mail over it by connecting to the smtp running on port 25.
But from some locations (university i.E.) I am unable to connect to port 25 (other ports work, I guess they do not want me to send spam-mails).
Of course, the smtp must continue running on port 25

So my question:
Can I somehow map some other port (port 26 i.E.) onto port 25?
So that when I connect to port 26, it's the same as connection to port 25?

Thanks!
nathan

[Januszzz]

Sure. You can use port forwarding and this can be obtained via several methods:
- netfilter configuration,
- netcat,
- gre tunnels I guess also?
- ssh.

The easiest for you will be ssh. Remember - you have to start it every time machine reboots:

ssh -f -N -L *:26:localhost:25 -l root localhost

That should do the trick

[LonelyStar]

Hi,

Thanks for your reply. There is a problem with the ssh methode. It makes a difference for smtp if I connect from localhost or from a foreign host. From localhost I can send mails to anyone without authentification. From a foreign host I can only send mails to local users.

I have to familiarizes myself with the suggestions in your list.

Greetings,
Nathan

[JeliJami]

You can also use xinetd to redirect to a different port.
Put xinetd in your default runlevel, and it will redirect at every boot.
Big advantage is that this method is session-less: every connection is a new connection.
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