Troubleshooting port blockage
Sometimes when installing an application on a server, users will run into the issue where the desired port is being blocked by another application. Rather than installing 3rd party software to determine what application is blocking the port, we can use tools that already come standard with Windows. Here we will discuss one way of determining what application is using what port.
There are two tools we will need:
- Command prompt
- Windows Task manager
For example let’s assume that a syslog application was installed on a server only to find out that port 514 is already in use. To determine what application is blocking the port we must perform the following steps:
1. First we notice that port 514 is already in use:
2. Bring up a command prompt and run the command netstat –a –o –p udp | find “514”
Notes:
- -a displays all connections and listening ports
- -o displays the process id (very important)
- -p displays the desired protocol (here we are interested in UDP)
- We can also specify the specific port of interest. Here we are interested in port 514
3. Note that the Process ID (PID) associated with the blocked port is 6724. Now we need to find out what application owns PID 6724. To do this we bring up the Windows Task Manager and under “View” and
“Select Columns…” select the option for “PID (Process Identifier).”
Next Click “Ok” and you will now see the PIDs displayed in Windows Task Manager.
4. When I search for the application associated with PID 6724 we can see that SyslogService.exe*32 is using port 514.
Our options are to either use the syslog server currently running or kill the PID which will make port 514 available.
