Opening a Port and Testing TCP Connections with PowerShell

🔌 Opening a Port and Testing TCP Connections with PowerShell

This example demonstrates how to use PowerShell and the [System.Net.Sockets.TcpListener] class to create a simple TCP listener on port 80 and accept incoming connections.

⚙️ 1. Create and Start a TCP Listener

The following code creates a listener on port 80. It accepts incoming connections and prints the remote IP address of the client.

$listener = [System.Net.Sockets.TcpListener]::new(80)
$listener.Start()
Write-Host "Listening on port 80..."

while ($true) {
    $client = $listener.AcceptTcpClient()
    Write-Host "Connection received: $($client.Client.RemoteEndPoint)"
    # Connection remains open; does not close client; keeps listening.
}
            

📝 Explanation

• $listener.Start(): Starts the listener and opens the port.
• AcceptTcpClient(): Accepts an incoming connection and returns a client object.
• Write-Host: Prints the IP and port of the remote client.
• This is a basic example; it does not handle disconnections or client cleanup.
• Ensure your firewall settings allow connections to the specified port (port 80).

🧪 2. Test the Connection

While the listener is running, you can test it using the following PowerShell command from the same machine or another machine on the same network:

Test-NetConnection -ComputerName localhost -Port 80
            

If the connection is successful, the listener will output a “Connection received” message.

💡 Summary

Opening a TCP port and testing incoming connections using PowerShell is straightforward. This script is a good starting point for understanding how TCP listeners work in PowerShell environments.