$tcp = New-Object System.Net.Sockets.TcpClient
$tcp.connect('servername or ip address', portnumber)
Or you can use this single line of code
(New-Object System.Net.Sockets.TcpClient).Connect('servername or ip address', portnumber)
There is also an in built powershell cmdlet that lets you test a port connection which only works with powershell 4.0
Test-NetConnection -Port portnumber -Computername 'Servername or ip address'
The first commands are much faster compared to the second one but does not give you any output.
The powershell cmdlet does give you a good output that you can use in another script but is much slower.