On Fri 01 Mar 2002, Theo Schmidt wrote:

> MODIFY_RESOLV_CONF to "no". I then wrote the two dns numbers:
> 
> nameserver 195.186.1.110
> nameserver 195.186.4.110
> 
> into /etc/resolv.conf so that they are now there permanently.
> 
> However, the behaviour of wwwoffle is still the same. I still get 

You did restart wwwoffle after making this change?

> "cannot open connection to xy on port 80".

Try first stopping wwwoffle. Then make a connection. Once the line is
up, try "host www.xy.com" (for whatever site you're trying to reach).
It should show something like:

www.xy.com              CNAME   xy.com
xy.com                  A       64.21.154.7

The first line doesn't have to be there, what's important is that there
is a line with an IP address.
If that works, start wwwoffle (while the line is still up). Then
wwwoffle should be able to connect to the website. If not, try
"telnet www.xy.com 80". It should say "Connected to xxxx". If not, then
the site simply isn't reachable. (If it is connected, it's reachable;
you can break the connection with ctrl-] q )

> I did try 8081 to no avail. I still don't understand what these ports 
> mean. I only know the 8080 which wwwoffle seems to be using and 631 
> which CUPS uses. I don't understand why wwwoffle wants to use port 80 
> and fails, nor what I should do about it. What is special about 9081 
> or 8082? Is there a good (newbie) reference on "ports" available?

Ports are simply a sort of channel. There's no special significance to a
specific number, besides the fact that ports below 1024 are considered
reserved for the superuser, to give some feeling of security, but now
with windows systems and linux systems at everyone's disposal so that
anyone can be the superuser there's not much security in those numbers.
It used to be different when systems connected to the internet were all
really big (and slow :-) systems administered by a trained staff.

Anyway, as I said, the numbers don't really mean anything. It's just
that there are agreements on what port numbers commonly carry what
specific services. For example, email (SMTP protocol) goes over port 25,
so if you connect to port 25 on a system you can be fairly confident
that there is an email system listening. HTTP is port 80, FTP is 21,
etc. 8080 is often used as a HTTP proxy, but that's not compulsory, it's
what is commonly used; it could be any number (even 80, or 25, or
12345).

If you get "cannot bind to port 8080: address already in use", that
means that there is already some other service on your system that is
listening to port 8080. It should be clear that only one service can
listen to a certain port at any given time, otherwise which service
should handle incoming connections to that port? You can find out what
is listening to a certain port with this (on linux systems):

$ netstat -anp | grep 8080
tcp     0      0 0.0.0.0:8080       0.0.0.0:* LISTEN   19091/wwwoffled     

Here you see that process number 19091 (called wwwoffled) is listening
to port 8080.

If you get "connection refused" when connecting to a port on some
system, it means that no service on that system is listening to that
port.


I guess this stuff is also explained in some FAQ. I did a quick look but
the first tcp/ip faq I found via Google is a bit too technical I think.
However, I'm sure a little searching will turn up something useful.


Paul Slootman

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