Closing Computer Ports

[Skeptikal]

Perhaps stupid questions...

-Does anyone know how to manualy (without firewall) close and open local computer ports ?
-Which port MSN Messenger uses?

Could someone kind enough explain that to me?

Thanks!

Skeptikal

[SiANiDE]

MSN uses two ports: 1863 and also port 80 (the HTTP port) for the ad at the bottom of the messenger window. In order to close the port (I assume you mean permanently) I am pretty certain you will have to use a firewall, whether it be hard or software is your choice. Why though, would you want to close a specific port?

[method]

Apparently there are no ways to manually shut ports in win2k/NT without a firewall...

Just going off replies to the same question elsewhere ;)

[SiANiDE]

Ah, /me forgot to mention, MSN uses several other ports:

6901 - Voice communications
6891-6900 - file transfer ports

By use of 10 ports for file transfer, this enables 10 simultaneous transfers (to separate users). The above ports do not connect to the msgr-XXNNN.msgr.hotmail.com server, they connect directly to the person you are communicating with (otherwise Microsoft could be liable for anything transferred, and also it would cost them £££ in bandwidth)

[Skeptikal]

Thanks for the replies...
Well I don't want to close the port permantly... I just wanted to make a program to close and open the MSN port "on demand"...
I have a LAN and shared computers (since I give "Home-Stay" services). I would like to be able to close and/or open the MSN port so the services could be, or not, used by some one.

But I would like to know a "general way" for closing any ports manualy... You seem to say that it is not possible :( too bad... I'll have to search a bit more a think...

Do you have any idea for my MSN stuff ?
Thanks.
Skepitkal.

[SiANiDE]

How does your network connect to the outside world?

[Skeptikal]

Hi !

I have a SuSE Linux gate-way to the internet (Cable connection).
6 computers (Windows XP or 98) connect to the geteway by a 10/100 ethernet LAN.

The Gateway computer used to be Windows XP pro (Can switch back to XP pro if it is easier to close ports ;) )

Thanks again.

[SiANiDE]

On CD2 of your SuSE package, there should be an app called SuSEfirewall (I think 3.1 is the latest). That's your best bet for blocking ports.

[Skeptikal]

Without using any firewall... would that be possible ?
(as i said.. to close the ports "manually")

[SiANiDE]

I think that the problem that you are going to run into here is that, by definition, this is (partially) the definition of a firewall. ie a peice of software which can control network access. It's a little like saying "how can I search the web without a search engine?".

With most firewalls, you can grant full access across all ports and allow all services, and then manually close them off as required. As far as actually switching a dip switch is concerned, this is not possible! (there are over 65,000 different ports to consider!)

As usual though, there are a couple of other ways you could try it, but in effect, they are still using a firewall, if you will. Try this:

1. Access your router via the RS-232 port and use the built in software (if it is there) to control access. This will only work if your router has this capability, and also it will not prevent access from your Linux box on that the particular port to the outside world. This is still using a flavour of firewall, albeit an "internal" one if you will.

Also, do you use Squid?

[psychotronic420]

Hey Skeptikal,

go check www.grc.com and see if they don't have the nfo your seeking.

[Skeptikal]

Thanks for the link !

I'm checking the site right now.

Thanks again.