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To test the port forwarding

Posted on 2006-06-22
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Last Modified: 2008-02-01
Is there any simple way to check whether ports are opened or not remotely?
If i do the telnet on public address with forwarded port number (in command prompt) and comes another blank screen, does that mean that port is forwarded correctly!
OR it really doesn't indicate port forwarding working correctly............is there any other simple way to check?

Thanks!
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Question by:joy333
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8 Comments
 
LVL 2

Expert Comment

by:Kalti
ID: 16966670
Depends on the port mate, if it goes to a blank screen that means the port is being accepted by something there is just no ASCII data transferable, so yes, that can be a good thing if the service you are forwarding is not required to answer with an ASCII message.

SMTP For instance will answer with something like this:

"220 SMTP service ready"

However, some services will just be blank... so, to answer your question; maybe. Hehe... depends on the service.
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LVL 11

Expert Comment

by:grsteed
ID: 16966751
As Kalti says it depends on the protocol being used. Usually if the screen goes blank you're OK.

If you are testing port 80 (http) entering /get followed by Enter will usually get you some HTML.

Cheers,

Gary
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LVL 4

Expert Comment

by:Phreonx
ID: 16967027
Hello,
you can use nmap from:

http://www.insecure.org/nmap/

to check for ports open remotely and a tcpwrapper [I'm arbitrarily assuming you are using linux or unix] that listens for port scans, like portsentry, to guard against abuse.

Hope that helped ;)

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Expert Comment

by:ded9
ID: 16967185
www.portforward.com

Check out this site

Reps
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Accepted Solution

by:
Rob Williams earned 30 total points
ID: 16968089
This tool will not work remotely, but if you have access to the site, CanYouSeeMe has a great on-line utility. You connect to their web site from the computer you want to check the port forwarding for, and then enter the particular port in the "test" box and it will verify if traffic on that port is forwarded correctly to the PC.
http://www.canyouseeme.org
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Author Comment

by:joy333
ID: 16992220
Yeah for common ports like 110, 25, 21, 23, 80 i can see the blank screen coming on. But if i can want to see special ports for example like Remote Desktop, Game server port how can i simply check.
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Assisted Solution

by:ded9
ded9 earned 20 total points
ID: 16992241
Download the software from this no1 software in the market for testing ports

http://www.gfi.com/lannetscan/?adclickid=7688151

Reps

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LVL 77

Expert Comment

by:Rob Williams
ID: 17069699
Thanks joy333,
--Rob
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