## PowerShell: Script To Telnet To Remote Hosts And Run Commands Against Them With Output To A File ##
## Overview: Useful for Telnet connections to Cisco Switches and other devices. Can add additional command strings
## Usage Examples: Add your environment specific details into the parameters below, or include when calling the script:
## ./Auth-Telnet.ps1 "127.0.0.1" "23" "admin" "password"

param(
    [string] $remoteHost = "10.64.80.15",
    [int] $port = 23,
    [string] $username = "****",
    [string] $password = "****",
    [int] $commandDelay = 1000
)

[string] $output = ""

## Read output from a remote host
function GetOutput
{
	## Create a buffer to receive the response
	$buffer = new-object System.Byte[] 1024
	$encoding = new-object System.Text.AsciiEncoding

	$outputBuffer = ""
	$foundMore = $false

	## Read all the data available from the stream, writing it to the
	## output buffer when done.
	do {
		## Allow data to buffer for a bit
		start-sleep -m $commandDelay

		## Read what data is available
		$foundMore = $false
		$stream.ReadTimeout = $commandDelay

		do {
			try {
				$read = $stream.Read($buffer, 0, 1024)

				if ($read -gt 0) {
					$foundMore = $true
					$outputBuffer += ($encoding.GetString($buffer, 0, $read))
				}
			} catch { $foundMore = $false; $read = 0 }
		} while ($read -gt 0)
	} while ($foundMore)

	$outputBuffer
}

function Main
{
	do {
	## Open the socket, and connect to the computer on the specified port
	Write-Host "Connecting to $remoteHost on port $port"

	trap { Write-Error "Could not connect to remote computer: $_"; exit }
	$socket = New-Object System.Net.Sockets.TcpClient($remoteHost, $port)

	# Write-Host "Connected. Press ^D followed by [ENTER] to exit.`n"
	Write-Host "Connected.`n"

	$stream = $socket.GetStream()
	$writer = New-Object System.IO.StreamWriter $stream

	## Receive the output that has buffered so far
	while (-not (GetOutput -match "Username:")) { sleep 1 }
	$writer.WriteLine($username)
	$writer.Flush()

	while (-not (GetOutput -match "Password:")) { sleep 1 }
	$writer.WriteLine($password)
	$writer.Flush()

	$SCRIPT:output += GetOutput

	## Close the streams
	$writer.Close()
	$stream.Close()

	$output
	$output | Out-File ".\$remoteHost.txt" #Change this to suit your environment
	} until ($SCRIPT:output -match "Authentication Successful")
}

Main