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Need to open ports

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Hi All:

Freshest of fresh meats here. My colleague and I are new to Linux and were tasked with setting up a mail server.

Installed Debian. Installed postfix. But now we are stuck because only ports 21, 22 & 23 are open (nmap -v).

My colleague deleted the iptables file. Iptables -L shows no rules.

How can we open ports 25, 80 and 110?

No external FW is involved.

Thanks in advance for your help.

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Re: Need to open ports

Submitted by pinniped on Thu, 2008-05-15 18:30.

Your server software should just be able to open a port if you have configured things correctly. Ports below 1024 are 'priviledged' - you need to be root to open them; if your server is properly configured but a port can't be opened, then something else is missing (one possibility is that the server may require the 'suid' bit to be set on the executable's file permissions).

You can see various logs in /var/log/ (dmesg, messages, kernel stuff etc)

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Re: Need to open ports

Submitted by Silentwing on Thu, 2008-05-15 20:16.

I understand the concept.
Our problem is a little more basic though: How do you open a port?
In all my searches I have not been able to find the actual command to open a port

Did I mention, I was fresh meat? :-)

Thanks in advance.

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Re: Need to open ports

Submitted by pinniped on Thu, 2008-05-15 23:58.

The ports are opened by the servers themselves and depends on their configuration; you shouldn't need to do any socket programming at all.
I suggest you read the manuals carefully and look at how each service needs to be configured to listen (which interfaces, what port to listen on, etc). There are two ways to run most services; one is to just start a 'daemon' on system startup (or manually if you've just installed it), and a process will run and listen for connections. The other way is to use 'inetd' (or xinetd and similar tools). 'inetd' has various control and configuration files, but basically it detects when someone attempts to connect to a specific port and then starts the appropriate daemon.

If you're talking about 'punching' a hole in a firewall that's a different matter - you'd have to talk to whoever maintains the firewall.

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