TCP Listener in PowerShell

Invoke-TcpListener.ps1

function Invoke-TcpListener {
    <#
    .SYNOPSIS
    Starts a TCP listener on a specified port.

    .DESCRIPTION
    This function starts a TCP listener on a specified port, accepts incoming connections,
    reads messages, and writes them to the terminal. It stops listening if the received
    message is "exit".

    .PARAMETER Port
    The port number on which the TCP listener should listen for incoming connections.

    .EXAMPLE
    Invoke-TcpListener -Port 5140

    Starts a TCP listener on port 5140.

    .NOTES
    Author: @joegasper -and GPT-4o
    Date: 2024-07-05
    #>

    [CmdletBinding()]
    param (
        [Parameter(Mandatory = $true)]
        [int]$Port
    )

    begin {
        # Initialize the TCP listener but do not start it
        $listener = New-Object System.Net.Sockets.TcpListener([System.Net.IPAddress]::Any, $Port)
        Write-Verbose "TCP Listener initialized on port ${Port}."
    }

    process {
        try {
            # Start the TCP listener
            $listener.Start()
            Write-Verbose "TCP Listener started."

            # Accept incoming connections and process them
            while ($true) {
                Write-Verbose "Waiting for incoming connections..."
                # Accept an incoming connection
                $client = $listener.AcceptTcpClient()
                Write-Verbose "Connection accepted."

                # Get the network stream from the client
                $stream = $client.GetStream()
                $reader = New-Object System.IO.StreamReader($stream, [System.Text.Encoding]::ASCII)
            
                # Read the incoming message
                $message = ""
                while ($null -ne ($line = $reader.ReadLine())) {
                    $message += $line + "`n"
                    if ($line -eq "") { 
                        break 
                    }
                    Write-Verbose "Message accepted."
                }
  
                # Write the message to the terminal
                Write-Host "`nReceived message:"
                Write-Host ($message.Trim() + "`n")

                # Close the client connection
                $client.Close()
 
                # Check if the message is "exit"
                if ($message -match "^exit\r?\n?$") {
                    Write-Host "`nExit command received. Stopping TCP Listener..."
                    break
                }
            }
        }
        catch {
            Write-Host "`nError: $_"
        }
    }
    end {
        # Stop the listener
        $listener.Stop()
        Write-Host "TCP Listener stopped."
    }
}