Cyber Security

PowerShell: Test open TCP Ports with Test-OpenPort (multiple hosts, multiple port numbers)

As the headline says, it’s all about port scanning today. When a computer sends SYN to another computer, the remote computer will usually answer with SYN + ACK or RST. By this fact, we can test if a port is open or not.

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Different port scanners can be used to test whether a port is open or not. Or Test-NetConnection or a self-created script. Remember Test NetConnection:

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But if you try to test multiple computers and multiple ports you are faced with an error message.

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The following function addresses this issue. Test-OpenPort allows testing multiple computers and multiple ports at once.

Test-OpenPort

Before we get to the function itself, I would like to show my function in action. The function has two parameters: Target and Port.


Test-OpenPort -Target 192.168.0.1 -Port 80

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These parameters are not named, so therefore you can omit the parameter names.


Test-OpenPort 192.168.0.1 80

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You can also omit the Target. The default value for this parameter is localhost.


Test-OpenPort -Port 80,443

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Running on multiple computers and ports requires the use of a comma.


Test-OpenPort 192.168.0.1,sid-500.com -Port 80,443

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The screen’s output is an object. Therefore you are able to customize this object with Select-Object or the Format-Commands (Format-Table …)


Test-OpenPort 192.168.0.1,sid-500.com -Port 80,443,53 | Sort-Object Status

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For a more sweeter view:


Test-OpenPort 192.168.0.1,sid-500.com -Port 80,443,53 | Sort-Object Status | Out-GridView

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The Function

Copy this function into your PowerShell ISE session and press the green start button.


function Test-OpenPort {

<# 

.SYNOPSIS
Test-OpenPort is an advanced Powershell function. Test-OpenPort acts like a port scanner. 

.DESCRIPTION
Uses Test-NetConnection. Define multiple targets and multiple ports. 

.PARAMETER
Target
Define the target by hostname or IP-Address. Separate them by comma. Default: localhost 

.PARAMETER
Port
Mandatory. Define the TCP port. Separate them by comma. 

.EXAMPLE
Test-OpenPort -Target sid-500.com,cnn.com,10.0.0.1 -Port 80,443 

.NOTES
Author: Patrick Gruenauer
Web:
https://sid-500.com 

.LINK
None. 

.INPUTS
None. 

.OUTPUTS
None.

#>

[CmdletBinding()]

param

(

[Parameter(Position=0)]
$Target='localhost',

[Parameter(Mandatory=$true, Position=1, Helpmessage = 'Enter Port Numbers. Separate them by comma.')]
$Port

)

$result=@()

foreach ($t in $Target)

{

foreach ($p in $Port)

{

$a=Test-NetConnection -ComputerName $t -Port $p -WarningAction SilentlyContinue

$result+=New-Object -TypeName PSObject -Property ([ordered]@{
'Target'=$a.ComputerName;
'RemoteAddress'=$a.RemoteAddress;
'Port'=$a.RemotePort;
'Status'=$a.tcpTestSucceeded

})

}

}

Write-Output $result

}

Make it permanent

If you like my approach open PowerShell ISE. Copy the function into your ISE session. Create a folder in C:\Program Files\Windows PowerShell\Modules and save the code as psm1 file. Make sure that your file name and folder name match.

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Close PowerShell. Open PowerShell again. The command is now available for all users. Have fun with Test-OpenPort!

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