functions/Invoke-Telnet.ps1
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Function Invoke-Telnet { <# .SYNOPSIS A powershell telnet client alternative. .DESCRIPTION A powershell telnet client alternative. Commands can also be sent in batch, or in interactive mode. .PARAMETER ComputerName This is a required parameter where you need to specify a computer name which can be localhost or a remote computer .PARAMETER Port This is a required parameter where you need to specify a TCP port you want to test connection on. .PARAMETER Timeout This is an optional parameter where you can specify the timeout in milli-seconds. Default timeout is 10000ms (10 seconds) .PARAMETER Commands This is an optional parameter where you can send in a string array of the commands to issue to the remote host when connected. If this parameter is omitted, you will be prompted for commands to send. .EXAMPLE Telnet -ComputerName DC1 -Port 3389 This command reports if DC1 can be connected on port 3389 which is default port for Remote Desktop Protocol (RDP). By simply running this command, you can check if Remote Desktop is enabled on computer DC1. .EXAMPLE Telnet WebServer 80 This command tells you if WebServer is reachable on Port 80 which is default port for HTTP. .EXAMPLE Get-Content C:\Computers.txt | Telnet -Port 80 This command will take all the computernames from a text file and pipe each computername to Telnet Cmdlet to report if all the computers are accessible on Port 80. .NOTES Original sources: - https://www.techtutsonline.com/powershell-alternative-telnet-command/ - https://www.leeholmes.com/blog/2009/10/28/scripting-network-tcp-connections-in-powershell/ Tim Cartwright: Updated to be interactive, also can optionally take a command list to be like a full featured telnet client #> [CmdletBinding()] param( [Parameter(Mandatory=$true, ValueFromPipeline=$true, ValueFromPipelineByPropertyName=$true)] [Alias ('HostName','cn','Host','Computer')] [String]$ComputerName, [Parameter(Mandatory=$true, ValueFromPipeline=$true, ValueFromPipelineByPropertyName=$true)] [int32]$Port, [int32] $Timeout = 10000, [string[]] $Commands ) begin { $commandPosition = 0 $commandCount = $Commands.Count ## Create a buffer to receive the response $buffer = new-object System.Byte[] 1024 $encoding = new-object System.Text.AsciiEncoding $outputBuffer = "" $foundMore = $false } Process { foreach($Computer in $ComputerName) { try { $tcp = New-Object System.Net.Sockets.TcpClient $connection = $tcp.BeginConnect($Computer, $Port, $null, $null) $connection.AsyncWaitHandle.WaitOne($timeout,$false) | Out-Null if ($tcp.Connected) { Write-InformationColored "Successfully connected to Host: `"$Computer`" on Port: `"$Port`"" -ForegroundColor Green $tcpStream = $tcp.GetStream() $tcpStream.ReadTimeout = 1000 $writer = New-Object System.IO.StreamWriter($tcpStream) $writer.AutoFlush = $true while ($command -ine "exit") { $outputBuffer = "" # Read all the data available from the stream, writing it to the outputbuffer when done. do { # Read what data is available $foundmore = $false do { try { $read = $tcpStream.Read($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 ($foundmore) # write the recieved data out to the host if (!([string]::IsNullOrWhiteSpace($outputBuffer))) { # remove the last LF char, and write the output out to the host Write-Information $outputBuffer.TrimEnd("`n") } $command = "" if ($Commands.Count -eq 0) { # prompt the user for the command to send $command = Read-Host -Prompt "Command" } else { # we got a command array, lets select the command out, and get ready to pick the next one if ($commandPosition -ge $commandCount) { break; } $command = $commands[$commandPosition]; $commandPosition++; # clean up the command so we can write it out $cmd = $command -replace "`r|`n", " " if ($cmd.Length -ge 80) { $cmd = $cmd.SubString(0, 80) + "..." } Write-InformationColored "Sending: $cmd" -ForegroundColor Yellow } # write the command back to the remote host if (!([string]::IsNullOrWhiteSpace($command))) { $writer.WriteLine($command); } } Write-InformationColored "`r`nDone." -ForegroundColor Yellow } else { Write-InformationColored "Could not connect to Host: `"$Computer `" on Port: `"$Port`"" -ForegroundColor Red } } catch { Write-InformationColored "Unknown Error: $($_)" -ForegroundColor Red } finally { if ($null -ne $writer) { $writer.Dispose(); } if ($null -ne $tcp) { $tcp.Dispose(); } } } } End {} } |