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user278604
Asked: 2015-08-12 22:45:49 +0800 CST

how to check if a port is blocked on a windows server

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I have a windows server 2008 machine which has qlikview application installed and this application has stopped working from last week, the application services were stopped. I'm unable to start the services(services are configured with the local account). As part of troubleshooting, I checked netstat to verify if the application ports are opened. I could not see on the list a couple of application related ports( eg. 4799, 4750). How do I verify if the ports are open or blocked on the server?

windows

2 Answers

  1. Hope this helps 9originally from elsewhere but fits your situation)

    Assuming that it's a TCP (rather than UDP) port that you're trying to use:

    1.On the server itself, use netstat -an to check to see which ports are listening

    2.From outside, just telnet host port (or telnet host:port on Unix systems) to see if the connection is refused, accepted, or timeouts

    On that latter test, then in general:

    • connection refused means that nothing is running on that port
    • accepted means that something is running on that port
    • timeout means that a firewall is blocking access
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  2. For scanning network hosts for service availability I would go with nmap. It's designed for this sort of job.

    nmap -pPORT IPADDRESS

    ... will tell you if the specified TCP port is open on the remote host. UDP scans may be performed with the -sU option. Nmap has many other options for port scanning and analysis that may be worth your time to investigate.

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