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Determining if a port is in use (1003971)

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Purpose

For troubleshooting purposes, it may be necessary to check if a port is already in use by a different application on your servers.

This article provides steps to use the Netstat and lsof utilities to check the ports in use and view the application that is utilizing the port.

Resolution

Checking port usage from Windows

To check the listening ports and applications with Netstat:

  1. Open a command prompt. For more information, see Opening a command or shell prompt (1003892).
  2. Run this command:

    netstat -bano

    You see output similar to:

    C:\netstat -bano | more 

    Proto    Local Address    Foreign Address    State        PID
    TCP      0.0.0.0:port     0.0.0.0:0          LISTENING    process ID
    [process.exe]
    TCP      0.0.0.0:port     0.0.0.0:0          LISTENING    process ID
    [process.exe]
    ...

    where:

    • process is the name of the application
    • port is the port that is being used
    • process ID is the process ID of the process

  3. If you see Can not obtain ownership information instead of the [process.exe] entry, you can find more information in the Windows Task Manager using the process ID:

    • Start Task Manager by pressing Ctrl+Shift+Esc
    • Click on the Processes tab and click View then Select Columns...
    • In the Select Process Page Columns window, click PID (Process Identifier), then click OK
    • You can then sort based on the PID column and find the PID number returned from the previous command

The output shows the processes that are listening, as well as the name of the process and process ID. When reviewing the information, only look at the ports that are listening to ensure that you find the correct application that is listening on that port. If you do not see any process listening for a port, that port is free to be utilized.

When you determine what is listening on the port, you must decide what action needs to be taken to resolve the conflict. This involves stopping a service or uninstalling the application that is utilizing the port.

For a list of ports used by VMware products, see  TCP and UDP Ports required to access VMware vCenter Server, VMware ESXi and ESX hosts, and other network components (1012382).

Checking port usage from Linux / Mac OS / ESX

Note: Mac OS and certain distributions of Linux do not support listing the process name with Netstat. If you are using Mac OS or are seeing errors on your distribution of Linux, follow the lsof instructions below.

To check the listening ports and applications with Netstat:

  1. Open a shell prompt. For more information, see Opening a command or shell prompt (1003892).
  2. In the shell prompt window, run this command:

    netstat -pan

    You see output similar to:

    [root@server]# netstat -pan

    Active Internet connections (servers and established)
    Proto Recv-Q Send-Q Local Address   Foreign Address State    PID/Program name
    tcp        0      0 0.0.0.0:port    0.0.0.0:*       LISTEN   process ID/process
    tcp        0      0 0.0.0.0:port    0.0.0.0:*       LISTEN   process ID/process

    ...

    where:

    • process is the name of the application
    • port is the port that is being used
    • process ID is the process ID of the process

To check the listening ports and applications with lsof:

  1. Open a shell prompt. For more information, see Opening a command or shell prompt (1003892).
  2. In the shell prompt window, run this command:

    lsof -i -P -n

    You see output similar to:

    [root@server]# lsof -i -P -n
    COMMAND   PID          USER   FD   TYPE   DEVICE SIZE   NODE  NAME
    process   process ID   root   3u   IPv4   3011          TCP   *:port (LISTEN)
    process   process ID   root   3u   IPv4   3011          TCP   *:port (LISTEN)
    ...


    where:

    • process is the name of the application
    • port is the port that is being used
    • process ID is the process ID of the process

The output from either of these two commands shows the processes that are listening, the name of the process, and the process ID. When reviewing the information it is important to only look at the ports that are listening to ensure that you find the correct application that is listening on that port. If you do not see any process listening for a port, than this means that it is free to be utilized.

When you determine what is listening on the port, you must decide what action needs to be taken to resolve the conflict. This involves stopping a service or uninstalling the application that is utilizing the port.

For a list of ports used by VMware products, see  TCP and UDP Ports required to access VMware vCenter Server, VMware ESXi and ESX hosts, and other network components (1012382).

Tags

port-availability  port-in-use  check-ports

See Also

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