Note. You can test only a TCP port connectivity by using the Test-NetConnection cmdlet. However, you cannot use the cmdlet to check the availability of the remote UDP ports.

ComputerName?????????? : ny-msg01
RemoteAddress????????? : 10.20.1.7
RemotePort???????????? : 25
InterfaceAlias???????? : CORP
SourceAddress????????? : 10.20.1.79
PingSucceeded????????? : True
PingReplyDetails (RTT) : 0 ms
TcpTestSucceeded?????? : True

Note. ?If the command returns PingSucceeded=False and TcpTestSucceeded= True, this most likely means that the ICMP Echo request (ping) is disabled on the remote computer.

Tip.?In earlier versions of Windows PowerShell (before version 4.0), you could check the availability of a remote TCP port with the command:

You can use the Test-NetConnection cmdlet to trace a route to a remote server by using the –TraceRoute parameter (similar to the built-in tracert command in Windows). You can limit the maximum number of hops during the route check by using the -Hops parameter.

Test-NetConnection ny-man01 –TraceRoute

Cmdlet returned a summary network access delay in milliseconds ? (PingReplyDetails (RTT): 41 ms) as well as all the IP addresses of the routers on the way to the destination host.

PowerShell: Check for Open Ports on Multiple Hosts

You can use PowerShell to check for the availability of a specific port on a number of remote computers.? Save the list of hostnames or IP addresses in a plain text file with the name servers.txt.

For example, your task is to find hosts where the TCP/25 port is not responding or is closed on a list of servers:

Get-Content c:\PS\list_servers.txt | ?where { -NOT (Test-Netconnection $_ -Port 25? -InformationLevel Quiet)}| Format-Table -AutoSize

You can use a simple monitoring PowerShell script that checks the availability of remote servers and displays a pop-up notification if any of the servers are unavailable.

For example, you can check the availability of basic services on all domain controllers during an AD health check (a DC list can be obtained with the Get-ADDomainController cmdlet). Let’s check the following services on the DC (there is a similar ‘Domain and trusts‘ rule in the PortQry tool):

• RPC – TCP/135
• LDAP – TCP/389
• LDAP – TCP/3268
• DNS – TCP/53
• Kerberos – TCP/88
• SMB – TCP/445

$Ports = "135","389","636","3268","53","88","445","3269", "80", "443"
$AllDCs = Get-ADDomainController -Filter * | Select-Object Hostname,Ipv4address
ForEach($DC in $AllDCs){
Foreach ($P in $Ports){
$check=Test-NetConnection $DC.Ipv4address -Port $P -WarningAction SilentlyContinue
If ($check.tcpTestSucceeded -eq $true)
{Write-Host $DC.hostname $P -ForegroundColor Green -Separator " => "}
else
{Write-Host $DC.hostname $P -Separator " => " -ForegroundColor Red}
}
}

The script checks the specified TCP ports on the domain controllers, and if any of the ports are unavailable, it highlights them in red (you can run this PowerShell script as a Windows service).

Simple TCP/IP Port Scanner in PowerShell

You can use PowerShell to implement a simple IP scanner that scans remote hosts or IP subnets for open/closed TCP ports.

To scan the range of IP addresses between 192.168.1.100 and 192.168.1.150 and display computers that have port 3389 open:

foreach ($ip in 100..150) {Test-NetConnection -Port 3389 -InformationLevel "Detailed" 192.168.1.$ip}

Scan a range of TCP ports (from 1 to 1024) on a remote host:

foreach ($port in 1..1024) {If (($a=Test-NetConnection srvfs01 -Port $port -WarningAction SilentlyContinue).tcpTestSucceeded -eq $true){ "TCP port $port is open!"}}

How to List Open Ports on Windows with PowerShell

Use the Get-NetTCPConnection cmdlet to list the ports that are open on the local computer (this is the PowerShell equivalent of NETSTAT). A list of all open TCP ports on the computer can be viewed as follows:

Get-NetTcpConnection -State Listen | Select-Object LocalAddress,LocalPort| Sort-Object -Property LocalPort | Format-Table

If you want to find out which program (process) is listening on a specific port on your computer, use the following command (where 443 is a port number you want to check):

Get-Process -Id (Get-NetTCPConnection -LocalPort 443).OwningProcess | ft Id, ProcessName, UserName, Path