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Old 04-24-2004, 07:09 AM   #1
insolution
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How can I "ping" a specific port?

Something has "broken" Remote Desktop between my home and work. I can't see my work computers from home as I could last week. Any suggestions for isolating the cause?

My home network/firewall/router has not changed. My work network/firewall/router has not changed (for a fact). RD works fine on both network locally, so there is a block on that port on the network between the two locations, right?

How can I ping a specific UDP port on the remote network to see if the packets are getting through, or how can I further diagnose this? Adlephia claims they are not filtering on that port and my work ISP isn't (we have multiple T1 lines with them, they're small and I have a good relationship with their NOC, so I'm sure it's not them).

I'm stumped (not that hard to do :-)

Scott
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Old 04-24-2004, 07:42 AM   #2
yellow
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Got fink installed? Install nmap.
No fink installation? Install fink, then install nmap.

Once installed, it'd be something like:
Code:
sudo nmap -sU -p# -v x.x.x.x
Where # = the port you want to check out, and x.x.x.x is the IP address.


Or, if the command line is not your cup of joe, try this (old) GUIfied version.

Last edited by yellow; 04-24-2004 at 07:46 AM.
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Old 04-24-2004, 11:01 AM   #3
insolution
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Thanks for the suggestion!

I tried to install nmap, but I get the following error:

Can't exec "make": No such file or directory at /sw/lib/perl5/Fink/Services.pm line 398.
### execution of make failed, exit code -1
Failed: compiling fink-0.19.2-1 failed


Any ideas? I'm not very unix-literate :-(

Scott

Last edited by insolution; 04-24-2004 at 11:10 AM.
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Old 04-24-2004, 11:09 AM   #4
hayne
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Did you install the Apple Developer Tools (XCode) ?
It is necessary to have them installed if you want to "install from source" in fink. That was a step that yellow omitted.
But isn't there a "binary" version of 'nmap' available from fink?
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Old 04-24-2004, 11:09 AM   #5
insolution
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So the port is open but RD doesn't work still

OK< I ran nmap via the GUI tool and got:

running nmap -sU -p 3283 -R -vv 216.242.83.17


Starting nmap V. 3.00 ( www.insecure.org/nmap/ )
Host host17.nasfm.org (216.242.83.17) appears to be up ... good.
Initiating UDP Scan against host17.nasfm.org (216.242.83.17)
The UDP Scan took 1 second to scan 1 ports.
Adding open port 3283/udp
Interesting ports on host17.nasfm.org (216.242.83.17):
Port State Service
3283/udp open unknown

Nmap run completed -- 1 IP address (1 host up) scanned in 2 seconds


So now I know that the port is open on the other end, but RD still doesn't see that computer (or any on that network). It's not RD as I tried from both my G4 and my TiBook.

Is there a way to send a UDP packet on port 3283 and see if it gets received? Any idea how to go about troubleshooting this?

Scott
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Old 04-24-2004, 11:23 AM   #6
hayne
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The standard way to troubleshoot networking problems is to use Ethereal to look at the packets sent & received. But understanding this might require some knowledge of the RD protocol. Try looking at it from a location where RD is working, then maybe you can recognize what is not working when you do it from your location.
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