From time to time it is necessary to check if specific TCP ports are open on remote servers. If you have many servers to check it can be a hassle to use telnet or other tools and check each server one by one. It is also often useful in other scripts to test if a remote server/port is alive before running code on them. To accomplish this I have written this little function.

function Test-PortAlive {
	#############################################################################################
	##Function:			Test-PortAlive
	##
	##Description:		Tests connection on a given server on a given port.
	##
	##Created by:		Noam Wajnman
	##Creation Date:	April 02, 2014	
	##############################################################################################
	[CmdletBinding()]
	[OutputType([System.boolean])]
	param(
		[Parameter(ValueFromPipeline=$true)][System.String[]]$server,
		[int]$port
	)
	$socket = new-object Net.Sockets.TcpClient
	$connect = $socket.BeginConnect($server, $port, $null, $null)
	$NoTimeOut = $connect.AsyncWaitHandle.WaitOne(500, $false)
	if ($NoTimeOut) {
		$socket.EndConnect($connect) | Out-Null
		return $true				
	}
	else {
		return $false
	}
}

The function takes two parameters $server and $port. $server is the name of the remote server to test and $port is the number of the TCP port to check the status of. The $server parameter can even be passed via the pipeline making it very easy to run. The function returns either $true or $false depending on whether the port is open or not. To avoid long wait times due to closed ports I have included a relatively short timeout value of 500 ms before the result is determined.
I have included a few examples below of how to call the function.
1. Normal

 
Test-PortAlive -port 135 "some_server" 

Here I just run the function as normal and pass both params. I chose port 135 in this example but it could be any port.
2. Pipeline

 
$Array_of_Server_Names | Test-PortAlive -port 135

In this example I am using an array to pass the server names to the function via the pipeline. I again chose port 135 in this example.

That’s it. I hope you find this function useful. Enjoy!!