Terminating a process running on local port using Powershell

Developers who work with frontend and backend often switching between tools get a message that a certain process is holding a port. For example, using the dotnet command, you can get a message that the address is already in use. Note - you usually must decide if you really want to terminate the process running on a certain port, but if you are sure that you just want to close the process and free up the local port for its use, it would be nice to have a way of
just closing the process running on that local port. A typical output would be:

 System.IO.IOException: Failed to bind to address http://127.0.0.1:5000: address already in use.

We can locate which process is using te port, that is, the local port, and then terminate the process. This will free up the local port so we can use it. Here is a Powershell function that will find the process running at a local port, if any, given by a specied port number.

<#
.SYNOPSIS
Stops the process using the specified local port 

.DESCRIPTION
This function finds the process, if any, using the specified port and stops it.
In case there are no process, the function exits.

.PARAMETER portId
The port number to check for the process

.RETURNS int
If successful, returns 0. If not, returns -1.

.EXAMPLE
Terminate-Port -portId 5000
#>
function Terminate-Port {
    param (
        [Parameter(Mandatory = $true)]
        [int]$portId
    )

    # Get the process ID (PID) using the specified port 
    try {
        Write-Host "Looking for processing running using local port: $portId"
        $connection = Get-NetTCPConnection -LocalPort $portId -ErrorAction Stop
        if ($connection) {
            Write-Output "Port $portId is in use by process ID $($connection.OwningProcess | Select-Object -Unique)."
        } else {
            Write-Output "Port $portId is not in use."
            return 0 | Out-Null
        }
    } catch {
        Write-Output "An error occurred: $_"
        return -1 | Out-Null
    }

    $processId = $connection.OwningProcess

    if ($processId -and $processId -gt 0) {
        $process = Get-Process -Id $processId
        if ($process) {
            # Stop the process
            try {
                Stop-Process -Id $processId -Force
                Write-Host "Process running at port $portId was terminated."
                return 0 | Out-Null
            } catch {
                Write-Host "Could not stop process. Reason: $error"
            }
        }
    }

    Write-Host "No process found using port $portId."
    return -1 | Out-Null
}

To terminate , we just run the command

 Terminate-Port -portId 5000

Screenshots of the function being run: BEFORE the command Terminate-Port is run and AFTER. Note that the process running at the given portId was terminated and then the local port is freed up again.

AFTER

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