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issue accessing sites using port 19, 21 and 25

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Occasional Advisor

issue accessing sites using port 19, 21 and 25

hi everyone,

I just want to know something regarding an “issue accessing sites using port 19, 21 and 25”.

I tried to use IE 6.0 and IE 7.0, create a local site and alter the ports as 1 to 25.. but there are 3 ports that i encountered that failed, 19, 21 and 25. Below are the results:

Yes = no problem accessing site
No = cannot access the site

everything else can be accessed but this:
Browser Port 19 Port 21 Port 25
__________________________

IE 6.0 Yes No No
__________________________
IE 7.0 No No No
__________________________
Mozilla
Firefox
2.0 No No No
__________________________

i still could not find relevant article on the web, no available article according to MS Support.

(There are some who claim that those ports are being blocked.)

by the way, in our company, it was just implemented that when we are doing a project, it would be saved into port 1, any progress in the project would lead into port 2, port 3, and so on. So it would mean that we would be using those ports that can't be accessed.

i would appreciate it if anyone can give me any expert advise why these are unusable port or give me any informative article that could give me an idea why these can't be used.

Thanks.
Regards,
Jonathan
7 REPLIES
Occasional Advisor

Re: issue accessing sites using port 19, 21 and 25

sorry for the table, i did not realized it would look like that..

ports that can't be accessed

ports 21 and 25 of IE 6.0
ports 19, 21 and 25 of IE 7.0
ports 19, 21 and 25 of Mozilla Firefox 2.0
Exalted Contributor

Re: issue accessing sites using port 19, 21 and 25

Shalom Jonathan,

Port 21 is ftp, and the IE browser does have an ftp client built in. So it should be able to access ports 20-21 and to FTP transfers. Not a great client but it is what it is.

Port 25 is smtp.

It is a severely abused port because it is attacked with spam and spam relay attempts. Therefore browsers are generally not going to be able to anything useful on port 25.

From your company to the outside world port 25 should be blocked, its a nearly criminal offense to leave this port open outbound on a firewall.

SEP
Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
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Occasional Advisor

Re: issue accessing sites using port 19, 21 and 25

thank you for the information you have given SEP,

i have a follow up question, feel free to answer everybody. :-)

now i know that those ports are blocked and can't be used, and now here comes the hard part. where can i find an article that tells me those ports are really blocked?

i found this article in mozilla: http://www.mozilla.org/projects/netlib/PortBanning.html

since i found out that mozilla is blocking the ports from the link above, this is the only question left:
Is there any article or website that explains the port banning of internet explorer?

i already know that other ports can't be used (thanks to SEP for his clarification on port 20, 21 and 25), i would appreciate it if anyone can give me links to "one or more websites" that answers my question above.

Thanks.
Regards,
Jonathan
Frequent Advisor

Re: issue accessing sites using port 19, 21 and 25

It is not that explorer will actually block ports. Explorer can be directed to use any port. The question is whether that port is available ( on the target and through the network ) and if the protocol is compatible with the browser.

As SEP said, most browsers will do both FTP, HTTP and HTTPS protocols. But if you point a browser to a port running a protocol the browser cannot communicate with, you will get no response.

For instance: If you port a web browser to port 23 ( telnet ) or 22 ( ssh ) the browser will not return any information.
http://www.hostname.com:23
http://www.hostname.com:22
ftp://www.hostname.com (default)
^^ ^^^^^^^^^^^^^^^ ^^
Protocol Address Port

By default, "http" in the address bar will tell it to go to port 80 ( depending on your settings ) the ":22" and ":23" actually perform the port redirect.

So your browser is not blocking any port typically, it just only works with certain protocols.

I hope this helps.
Honored Contributor

Re: issue accessing sites using port 19, 21 and 25

One issue you may be running into is that you are trying to (I think) run a web server on a non standard port that is a "Well Known Port" for something else. In your case, you are choosing WKPs for very common, sometimes very important daemons

If you want to run a web server on a non-standard port, you'll have to run it on a port number greater than 1023. Common nonstandard web ports include 8080, 8088, 8000, and 8001.

Please read this: http://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers
Occasional Advisor

Re: issue accessing sites using port 19, 21 and 25

hi everyone,

i think i already understand the part where these ports can't be used. thanks for those very useful information.

i don't think my boss would believe it comming from a word of mouth, i think it would be better if i present an article and proudly tell him that those ports can't be used.

can anyone help me get an article from any website that validates this issue?

Thanks.
Regards,
Jonathan
Occasional Advisor

Re: issue accessing sites using port 19, 21 and 25

How about http://www.w3.org/Daemon/User/Installation/PrivilegedPorts.html

Just google for privileged ports. Any port under 1024 is privileged, which means a normal user cannot use it, only root. You can also look at /etc/services, which defines known ports.
Omne animal triste post coitum
//Add this to "OnDomLoad" event