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Any idea what can block certain port on win7

Posted on 2014-03-07
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Last Modified: 2014-03-28
We have users complaining that their software uses ports in the 20002, 20000-20100, and/or 11444 range.

We cannot figure out what is blocking the ports.  We ran netstat -an and it doesn't show the   port as blocked.

The user says they use GDB agent (what ever that is) to send a system call to open the port 20002 and it fails. But works for ports 20000 and 20001.

Any thought on how to figure this out. I'm lost on this.

Thanks
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Question by:rdefino
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8 Comments
 
LVL 13

Accepted Solution

by:
Santosh Gupta earned 1000 total points
ID: 39913759
Hi,

Try this,

1. go to other machine and run CMD and type "telnet yourwin7ip portnumber" and see if port is really blocked.

2. go to windows firewall and see if there is any rule created to block these ports.
http://www.dummies.com/how-to/content/how-to-open-a-port-in-the-windows-7-firewall.html

3. Check if have any antivirus that may block these ports.

4. just for testing disable windows firewall and antivirus one by one and see.
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Author Comment

by:rdefino
ID: 39913777
When you say "yourwin7ip", you mean the ip of the system we believe the has the port blocked?

Also, firewall is disabled and antivirus has been removed.
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Expert Comment

by:Santosh Gupta
ID: 39913783
yes,  ip of the system we believe the has the port blocked.
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Author Comment

by:rdefino
ID: 39913796
It fails, but it fails for any port I try.
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LVL 13

Expert Comment

by:Santosh Gupta
ID: 39913808
1. are you able to ping the effected machine, from the machine where are you trying to telnet.
2. Do you have VLAN configured,
3. pls try to change the switch port of effected machine.
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LVL 82

Expert Comment

by:David Johnson, CD, MVP
ID: 39913896
GDB Agent is the Gnu Debugger Agent.  You may want to set a rule that allows it on the local network. Rather than go port by port
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Author Comment

by:rdefino
ID: 39913903
Set the rule where for GDB?
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LVL 10

Assisted Solution

by:Pramod Ubhe
Pramod Ubhe earned 1000 total points
ID: 39917116
some inputs from my side -

1. Windows firewall and antivirus can block ports
2. Widows will not start listening on any port unless there is any application configured to use that specific port so your telnet output may show that it is not listening for that particular port. Make sure that your application is configured correctly for using those ports and it running.
3. netstat -bano > result.txt command can show you existing ports configured and or the ones which are being used. Make sure that there is no other application/service is using ports required for your application.
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