How to Close TCP and UDP Ports via Windows Command Line

When a port is in use on Windows, you might need to close it to free it for another application, resolve conflicts, or improve security. Unlike Linux where you can directly kill processes bound to ports, Windows requires identifying the process first, then either stopping it or blocking the port via firewall rules.

This guide shows you how to find what's using a port and close it using Windows command-line tools.

TLDR

Find the process using a port with netstat -ano | findstr :PORT, then kill it with taskkill /PID <pid> /F. To block a port with Windows Firewall, use netsh advfirewall firewall add rule to create a blocking rule. For services, use net stop or sc stop to stop the service listening on the port.

Prerequisites

You need administrative privileges (Run as Administrator) for most port-closing operations. Basic familiarity with Windows Command Prompt or PowerShell helps.

Finding What's Using a Port

Before closing a port, identify which process is using it.

Using netstat

netstat -ano | findstr :8080

Output:

TCP    0.0.0.0:8080           0.0.0.0:0              LISTENING       4532
TCP    [::]:8080              [::]:0                 LISTENING       4532

The last column (4532) is the Process ID (PID).

Using PowerShell

Get-NetTCPConnection -LocalPort 8080

Output shows more detail:

LocalAddress  LocalPort RemoteAddress RemotePort State       OwningProcess
------------  --------- ------------- ---------- -----       -------------
0.0.0.0       8080      0.0.0.0       0          Listen      4532

Identify the Process Name

Once you have the PID, find which program it is:

tasklist | findstr 4532

Output:

node.exe                      4532 Console                    1     45,234 K

Or get more details with PowerShell:

Get-Process -Id 4532

Killing the Process

Once you know the PID, terminate the process to free the port.

Using taskkill

taskkill /PID 4532 /F

The /F flag forces termination.

Or kill by process name:

taskkill /IM node.exe /F

This kills all instances of node.exe.

Using PowerShell

Stop-Process -Id 4532 -Force

Or by name:

Stop-Process -Name "node" -Force

Verify Port is Closed

netstat -ano | findstr :8080

No output means the port is now free.

Stopping Windows Services

If a Windows Service is using the port, stop the service rather than killing the process.

Find the Service

sc query | findstr /C:"SERVICE_NAME"

Or use PowerShell to find services by PID:

Get-WmiObject Win32_Service | Where-Object {$_.ProcessId -eq 4532} | Select Name, DisplayName

Stop the Service

net stop "Service Name"

Or using sc:

sc stop ServiceName

PowerShell alternative:

Stop-Service -Name "ServiceName"

Common Services and Ports

# Stop IIS (uses port 80/443)
iisreset /stop

# Stop SQL Server (port 1433)
net stop MSSQLSERVER

# Stop Remote Desktop (port 3389)
net stop TermService

Blocking Ports with Windows Firewall

Instead of killing processes, block ports using firewall rules.

Block Inbound Traffic on a Port

netsh advfirewall firewall add rule name="Block Port 8080" dir=in action=block protocol=TCP localport=8080

This prevents any inbound connections to port 8080.

Block Outbound Traffic

netsh advfirewall firewall add rule name="Block Outbound 8080" dir=out action=block protocol=TCP localport=8080

Block UDP Port

netsh advfirewall firewall add rule name="Block UDP 53" dir=in action=block protocol=UDP localport=53

Remove Firewall Rule

netsh advfirewall firewall delete rule name="Block Port 8080"

List All Firewall Rules

netsh advfirewall firewall show rule name=all

Or filter for specific port:

netsh advfirewall firewall show rule name=all | findstr 8080

PowerShell Firewall Management

Block a Port

New-NetFirewallRule -DisplayName "Block Port 8080" -Direction Inbound -LocalPort 8080 -Protocol TCP -Action Block

Remove Rule

Remove-NetFirewallRule -DisplayName "Block Port 8080"

List Rules

Get-NetFirewallRule | Where-Object {$_.LocalPort -eq 8080}

Closing Specific Application Ports

Stop Web Servers

IIS (Internet Information Services):

# Stop IIS
iisreset /stop

# Or stop specific site
%windir%\system32\inetsrv\appcmd stop site "Default Web Site"

Apache:

# Stop Apache service
net stop Apache2.4

# Or if running from command line
httpd -k stop

Stop Database Servers

SQL Server:

net stop MSSQLSERVER

MySQL:

net stop MySQL80

PostgreSQL:

net stop postgresql-x64-13

Stop Development Servers

Node.js applications:

# Find all node processes
tasklist | findstr node.exe

# Kill them
taskkill /IM node.exe /F

Python Flask/Django:

tasklist | findstr python.exe
taskkill /IM python.exe /F

Handling "Access Denied" Errors

If you get "Access Denied" when trying to kill a process:

1. Run as Administrator: Right-click Command Prompt or PowerShell and select "Run as administrator"

2. Check if it's a system process: Some processes are protected. Use Process Explorer to see if it's a critical system process.

3. Stop the parent service: If the process is started by a service, stop the service instead.

Preventing Processes from Restarting

Some processes automatically restart. To prevent this:

Disable the Service

sc config ServiceName start= disabled
net stop ServiceName

Change Application Startup

For applications that start automatically:

1. Open Task Manager (Ctrl+Shift+Esc)
2. Go to Startup tab
3. Disable the application

Or via command line:

Get-CimInstance -ClassName Win32_StartupCommand | Select-Object Name, Location, Command

Troubleshooting Common Issues

Port Still Shows as Listening

After killing a process, the port might remain in TIME_WAIT:

netstat -ano | findstr :8080

Output:

TCP    127.0.0.1:8080    127.0.0.1:54321    TIME_WAIT       0

TIME_WAIT connections clear automatically within 30-120 seconds. To force it:

# Restart TCP/IP stack (requires admin)
netsh int ip reset

Then restart your computer.

Multiple Processes on Same Port

If multiple processes share a port:

netstat -ano | findstr :80

Kill each PID:

taskkill /PID 1234 /F
taskkill /PID 5678 /F

Cannot Find Process

If netstat shows a port in use but you can't find the process:

# Show all processes including system
netstat -anob

The -b flag shows the executable name (requires admin).

Automating Port Cleanup

PowerShell Script to Kill Process on Port

# kill-port.ps1
param([int]$Port)

$process = Get-NetTCPConnection -LocalPort $Port -ErrorAction SilentlyContinue | Select-Object -ExpandProperty OwningProcess -Unique

if ($process) {
    Stop-Process -Id $process -Force
    Write-Host "Killed process $process using port $Port"
} else {
    Write-Host "No process found using port $Port"
}

Usage:

.\kill-port.ps1 -Port 8080

Batch Script

@echo off
REM kill-port.bat
SET PORT=%1

FOR /F "tokens=5" %%P IN ('netstat -ano ^| findstr :%PORT%') DO (
    taskkill /PID %%P /F
)

Usage:

kill-port.bat 8080

Security Considerations

Don't kill critical system processes: Processes like svchost.exe, System, or csrss.exe are critical. Killing them can crash Windows.

Check what you're stopping: Before killing a process, verify it's safe to terminate.

Use firewall rules for security: If you want to prevent access to a port, use firewall rules rather than constantly killing processes.

Monitor for malware: If unknown processes are binding to ports, scan for malware.

Closing ports on Windows involves finding the process using the port and either terminating it, stopping its service, or blocking the port via firewall rules. Use netstat or PowerShell to identify the process, taskkill or Stop-Process to terminate it, and netsh or New-NetFirewallRule to block ports. Always verify you're not stopping critical system processes before proceeding.