New answer, powershell

TCP

Get-Process -Id (Get-NetTCPConnection -LocalPort YourPortNumberHere).OwningProcess

UDP

Get-Process -Id (Get-NetUDPEndpoint -LocalPort YourPortNumberHere).OwningProcess

Old answer, cmd

 C:\> netstat -a -b

(Add -n to stop it trying to resolve hostnames, which will make it a lot faster.)

Note Dane's recommendation for TCPView. It looks very useful!

-a Displays all connections and listening ports.

-b Displays the executable involved in creating each connection or listening port. In some cases well-known executables host multiple independent components, and in these cases the sequence of components involved in creating the connection or listening port is displayed. In this case the executable name is in [] at the bottom, on top is the component it called, and so forth until TCP/IP was reached. Note that this option can be time-consuming and will fail unless you have sufficient permissions.

-n Displays addresses and port numbers in numerical form.

-o Displays the owning process ID associated with each connection.

There's a native GUI for Windows:

• Start menu All Programs Accessories System Tools Resource Monitor

• or run resmon.exe,

• or from TaskManager Performance tab.

For Windows:

netstat -aon | find /i "listening"

Use TCPView if you want a GUI for this. It's the old Sysinternals application that Microsoft bought out.

The -b switch mentioned in most answers requires you to have administrative privileges on the machine. You don't really need elevated rights to get the process name!

Find the pid of the process running in the port number (e.g., 8080)

netstat -ano | findStr "8080"

Find the process name by pid

tasklist /fi "pid eq 2216"

You can get more information if you run the following command:

netstat -aon | find /i "listening" |find "port"

using the 'Find' command allows you to filter the results. find /i "listening" will display only ports that are 'Listening'. Note, you need the /i to ignore case, otherwise you would type find "LISTENING". | find "port" will limit the results to only those containing the specific port number. Note, on this it will also filter in results that have the port number anywhere in the response string.

1. Open a command prompt window (as Administrator) From "Start\Search box" Enter "cmd" then right-click on "cmd.exe" and select "Run as Administrator"

2. Enter the following text then hit Enter.

   netstat -abno

   -a Displays all connections and listening ports.

   -b Displays the executable involved in creating each connection or listening port. In some cases well-known executables host multiple independent components, and in these cases the sequence of components involved in creating the connection or listening port is displayed. In this case the executable name is in [] at the bottom, on top is the component it called, and so forth until TCP/IP was reached. Note that this option can be time-consuming and will fail unless you have sufficient permissions.

   -n Displays addresses and port numbers in numerical form.

   -o Displays the owning process ID associated with each connection.

3. Find the Port that you are listening on under "Local Address"

4. Look at the process name directly under that.

NOTE: To find the process under Task Manager

1. Note the PID (process identifier) next to the port you are looking at.

2. Open Windows Task Manager.

3. Select the Processes tab.

4. Look for the PID you noted when you did the netstat in step 1.

   • If you dont see a PID column, click on View / Select Columns. Select PID.

   • Make sure Show processes from all users is selected.

Get PID and Image Name

Use only one command:

for /f "tokens=5" %a in ('netstat -aon ^| findstr 9000') do tasklist /FI "PID eq %a"

where 9000 should be replaced by your port number.

The output will contain something like this:

Image Name                     PID Session Name        Session#    Mem Usage
========================= ======== ================ =========== ============
java.exe                      5312 Services                   0    130,768 K

---

Explanation:

• it iterates through every line from the output of the following command:

  netstat -aon | findstr 9000
  

• from every line, the PID (%a - the name is not important here) is extracted (PID is the 5^th element in that line) and passed to the following command

  tasklist /FI "PID eq 5312"
  

---

If you want to skip the header and the return of the command prompt, you can use:

echo off & (for /f "tokens=5" %a in ('netstat -aon ^| findstr 9000') do tasklist /NH /FI "PID eq %a") & echo on

Output:

java.exe                      5312 Services                   0    130,768 K

First we find the process id of that particular task which we need to eliminate in order to get the port free:

Type

netstat -n -a -o

After executing this command in the Windows command line prompt (cmd), select the pid which I think the last column. Suppose this is 3312.

Now type

taskkill /F /PID 3312

You can now cross check by typing the netstat command.

NOTE: sometimes Windows doesnt allow you to run this command directly on CMD, so first you need to go with these steps:

From the start menu -> command prompt (right click on command prompt, and run as administrator)

With PowerShell 5 on Windows 10 or Windows Server 2016, run Get-NetTCPConnection cmdlet. I guess that it should also work on older Windows versions.

The default output of Get-NetTCPConnection does not include Process ID for some reason and it is a bit confusing. However, you could always get it by formatting the output. The property you are looking for is OwningProcess.

• If you want to find out the ID of the process that is listening on port 443, run this command:

    PS C:\> Get-NetTCPConnection -LocalPort 443 | Format-List
  
    LocalAddress   : ::
    LocalPort      : 443
    RemoteAddress  : ::
    RemotePort     : 0
    State          : Listen
    AppliedSetting :
    OwningProcess  : 4572
    CreationTime   : 02.11.2016 21:55:43
    OffloadState   : InHost
  

• Format the output to a table with the properties you look for:

    PS C:\> Get-NetTCPConnection -LocalPort 443 | Format-Table -Property LocalAddress, LocalPort, State, OwningProcess
  
    LocalAddress LocalPort  State OwningProcess
    ------------ ---------  ----- -------------
    ::                 443 Listen          4572
    0.0.0.0            443 Listen          4572
  

• If you want to find out a name of the process, run this command:

    PS C:\> Get-Process -Id (Get-NetTCPConnection -LocalPort 443).OwningProcess
  
    Handles  NPM(K)    PM(K)      WS(K)     CPU(s)     Id  SI ProcessName
    -------  ------    -----      -----     ------     --  -- -----------
    143      15     3448      11024              4572   0 VisualSVNServer
  

To get a list of all the owning process IDs associated with each connection:

netstat -ao |find /i "listening"

If want to kill any process have the ID and use this command, so that port becomes free

Taskkill /F /IM PID of a process

It is very simple to get the port number from a PID in Windows.

The following are the steps:

1. Go to run type cmd press Enter.

2. Write the following command...

   netstat -aon | findstr [port number]
   

   (Note: Don't include square brackets.)

3. Press Enter...

4. Then cmd will give you the detail of the service running on that port along with the PID.

5. Open Task Manager and hit the service tab and match the PID with that of the cmd, and that's it.

netstat -aof | findstr :8080 (Change 8080 for any port)

To find out which specific process (PID) is using which port:

netstat -anon | findstr 1234

Where 1234 is the PID of your process. [Go to Task Manager Services/Processes tab to find out the PID of your application.]

Just open a command shell and type (saying your port is 123456):

netstat -a -n -o | find "123456"

You will see everything you need.

The headers are:

 Proto  Local Address          Foreign Address        State           PID
 TCP    0.0.0.0:37             0.0.0.0:0              LISTENING       1111

This is as mentioned here.

In case someone need an equivalent for macOS like I did, here is it:

lsof -i tcp:8080

After you get the PID of the process, you can kill it with:

kill -9 <PID>

If you'd like to use a GUI tool to do this there's Sysinternals' TCPView.

1. Open the command prompt - start Run cmd, or start menu All Programs Accessories Command Prompt.

2. Type

   netstat -aon | findstr '[port_number]'
   

Replace the [port_number] with the actual port number that you want to check and hit Enter.

3. If the port is being used by any application, then that applications detail will be shown. The number, which is shown at the last column of the list, is the PID (process ID) of that application. Make note of this.

4. Type

   tasklist | findstr '[PID]'
   

Replace the [PID] with the number from the above step and hit Enter.

5. Youll be shown the application name that is using your port number.

Netstat:

• -a displays all connection and listening ports
• -b displays executables
• -n stop resolve hostnames (numerical form)

• -o owning process

  netstat -bano | findstr "7002"
  
  netstat -ano > ano.txt 
  

The Currports tool helps to search and filter

Type in the command: netstat -aon | findstr :DESIRED_PORT_NUMBER

For example, if I want to find port 80: netstat -aon | findstr :80

This answer was originally posted to this question.

netstat -ao and netstat -ab tell you the application, but if you're not a system administrator you'll get "The requested operation requires elevation".

It's not ideal, but if you use Sysinternals' Process Explorer you can go to specific processes' properties and look at the TCP tab to see if they're using the port you're interested in. It is a bit of a needle and haystack thing, but maybe it'll help someone...

I recommend CurrPorts from NirSoft.

CurrPorts can filter the displayed results. TCPView doesn't have this feature.

Note: You can right click a process's socket connection and select "Close Selected TCP Connections" (You can also do this in TCPView). This often fixes connectivity issues I have with Outlook and Lync after I switch VPNs. With CurrPorts, you can also close connections from the command line with the "/close" parameter.

A single-line solution that helps me is this one. Just substitute 3000 with your port:

$P = Get-Process -Id (Get-NetTCPConnection -LocalPort 3000).OwningProcess; Stop-Process $P.Id

Edit: Changed kill to Stop-Process for more PowerShell-like language

To find pid who using port 8000

netstat -aon | findstr '8000'

To Kill that Process in windows

taskkill /pid pid /f

where pid is the process id which you get form first command

Follow these tools: From cmd: C:\> netstat -anob with Administrator privileges.

Process Explorer

Process Dump

Port Monitor

All from sysinternals.com.

If you just want to know process running and threads under each process, I recommend learning about wmic. It is a wonderful command-line tool, which gives you much more than you can know.

Example:

c:\> wmic process list brief /every:5

The above command will show an all process list in brief every 5 seconds. To know more, you can just go with /? command of windows , for example,

c:\> wmic /?
c:\> wmic process /?
c:\> wmic prcess list /?

And so on and so forth. :)

Using Windows' default shell (powershell) and without external apps

For those using PowerShell, try Get-NetworkStatistics:

> Get-NetworkStatistics | where Localport -eq 8000


ComputerName  : DESKTOP-JL59SC6
Protocol      : TCP
LocalAddress  : 0.0.0.0
LocalPort     : 8000
RemoteAddress : 0.0.0.0
RemotePort    : 0
State         : LISTENING
ProcessName   : node
PID           : 11552

Use:

netstat -a -o

This shows the PID of the process running on a particular port.

Keep in mind the process ID and go to Task Manager and services or details tab and end the process which has the same PID.

Thus you can kill a process running on a particular port in Windows.

Programmatically, you need stuff from iphlpapi.h, for example GetTcpTable2(). Structures like MIB_TCP6ROW2 contain the owner PID.

Using PowerShell... ...this would be your friend (replace 8080 with your port number):

 netstat -abno | Select-String -Context 0,1 -Pattern 8080

Sample output

>   TCP    0.0.0.0:8080           0.0.0.0:0              LISTENING         2920
   [tnslsnr.exe]
>   TCP    [::]:8080              [::]:0                 LISTENING         2920
   [tnslsnr.exe]

So in this example tnslsnr.exe (OracleXE database) is listening on port 8080.

Quick explanation

• Select-String is used to filter the lengthy output of netstat for the relevant lines.
• -Pattern tests each line against a regular expression.
• -Context 0,1 will output 0 leading lines and 1 trailing line for each pattern match.

You can also check the reserved ports with the command below. Hyper-V reserve some ports, for instance.

netsh int ipv4 show excludedportrange protocol=tcp