(PowerShell) FTP through SSH Tunnel with Dynamic Port Forwarding

Demonstrates how to start a background thread that runs a portable SSH tunnel w/ dynamic port forwarding that the foreground thread can be used for establishing FTP sessions through an SSH tunnel.

Note: Some developers may be accustomed to starting an stunnel.exe proxy from https://www.stunnel.org. The stunnel.exe is not necessary here. Chilkat's background thread fulfills the task of what the external stunnel.exe does. Therefore, your application is self-contained, meaning that it can run anywhere because the SSH tunnel proxy is built-in.

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Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

# Starting in v9.5.0.49, all Chilkat classes can be unlocked at once at the beginning of a program
# by calling UnlockBundle.  It requires a Bundle unlock code.
$chilkatGlob = New-Object Chilkat.Global
$success = $chilkatGlob.UnlockBundle("Anything for 30-day trial.")
if ($success -ne $true) {
    $($chilkatGlob.LastErrorText)
    exit
}

# This example requires Chilkat version 9.5.0.50 or greater.
$tunnel = New-Object Chilkat.SshTunnel

$sshHostname = "sftp.example.com"
$sshPort = 22

# Connect to an SSH server and establish the SSH tunnel:
$success = $tunnel.Connect($sshHostname,$sshPort)
if ($success -ne $true) {
    $($tunnel.LastErrorText)
    exit
}

# Authenticate with the SSH server via a login/password
# or with a public key.  
# This example demonstrates SSH password authentication.
$success = $tunnel.AuthenticatePw("mySshLogin","mySshPassword")
if ($success -ne $true) {
    $($tunnel.LastErrorText)
    exit
}

# Indicate that the background SSH tunnel thread will behave as a SOCKS proxy server
# with dynamic port forwarding:
$tunnel.DynamicPortForwarding = $true

# We may optionally require that connecting clients authenticate with our SOCKS proxy server.
# To do this, set an inbound username/password.  Any connecting clients would be required to 
# use SOCKS5 with the correct username/password.
# If no inbound username/password is set, then our SOCKS proxy server will accept both
# SOCKS4 and SOCKS5 unauthenticated connections.

$tunnel.InboundSocksUsername = "chilkat123"
$tunnel.InboundSocksPassword = "password123"

# Start the listen/accept thread to begin accepting SOCKS proxy client connections.
# Listen on port 1080.
$success = $tunnel.BeginAccepting(1080)
if ($success -ne $true) {
    $($tunnel.LastErrorText)
    exit
}

# Now that a background thread is running a SOCKS proxy server that forwards connections
# through an SSH tunnel, it is possible to use any Chilkat implemented protocol that is SOCKS capable,
# such as HTTP, POP3, SMTP, IMAP, FTP, etc.  The protocol may use SSL/TLS because the SSL/TLS
# will be passed through the SSH tunnel to the end-destination.  Also, any number of simultaneous
# connections may be routed through the SSH tunnel.

$ftp = New-Object Chilkat.Ftp2

# Indicate that the HTTP object is to use our portable SOCKS proxy/SSH tunnel running in our background thread.
$ftp.SocksHostname = "localhost"
# The SocksPort must equal the port passed to BeginAccepting above.
$ftp.SocksPort = 1080
$ftp.SocksVersion = 5
# The SOCKS5 login/password set here must equal the InboundSocksUsername/Password set above.
$ftp.SocksUsername = "chilkat123"
$ftp.SocksPassword = "password123"

# This is the actual FTP server domain or IP address, and the login/password for the user account on the destination FTP server.
$ftp.Hostname = "ftp.someFtpServer.com"
$ftp.Username = "myLogin"
$ftp.Password = "myPassword"
$ftp.AuthTls = $true

# Connect and login (via the SSH tunnel) to the FTP server.
$success = $ftp.Connect()
if ($success -ne $true) {
    $($ftp.LastErrorText)
    exit
}

# Change to the remote directory where the file is located.
# This step is only necessary if the file is not in the root directory
# for the FTP account.
$success = $ftp.ChangeRemoteDir("junk")
if ($success -ne $true) {
    $($ftp.LastErrorText)
    exit
}

$localFilename = "c:/temp/hamlet.xml"
$remoteFilename = "hamlet.xml"

# Download a file.  (the data connection is also automatically established through the 
# SSH tunnel using dynamic port forwarding..)
$success = $ftp.GetFile($remoteFilename,$localFilename)
if ($success -ne $true) {
    $($ftp.LastErrorText)
    exit
}

# The disconnect is disconnecting with the FTP server and closes the SSH tunnel.
# The background tunnel thread is still running, and may be used for subsequent FTP connections,
# or even connections for any other purpose, such as HTTP, IMAP, SMTP, POP3, etc.
$success = $ftp.Disconnect()

# When the app is finished with the tunnel, it can cleanup..

# Stop the background listen/accept thread:
$waitForThreadExit = $true
$success = $tunnel.StopAccepting($waitForThreadExit)
if ($success -ne $true) {
    $($tunnel.LastErrorText)
    exit
}

# Close the SSH tunnel (would also kick any remaining connected clients).
$success = $tunnel.CloseTunnel($waitForThreadExit)
if ($success -ne $true) {
    $($tunnel.LastErrorText)
    exit
}