(Ruby) 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.

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

# 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 = Chilkat::CkGlobal.new()
success = chilkatGlob.UnlockBundle("Anything for 30-day trial.")
if (success != true)
    print chilkatGlob.lastErrorText() + "\n";
    exit
end

# This example requires Chilkat version 9.5.0.50 or greater.
tunnel = Chilkat::CkSshTunnel.new()

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

# Connect to an SSH server and establish the SSH tunnel:
success = tunnel.Connect(sshHostname,sshPort)
if (success != true)
    print tunnel.lastErrorText() + "\n";
    exit
end

# 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 != true)
    print tunnel.lastErrorText() + "\n";
    exit
end

# Indicate that the background SSH tunnel thread will behave as a SOCKS proxy server
# with dynamic port forwarding:
tunnel.put_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.put_InboundSocksUsername("chilkat123")
tunnel.put_InboundSocksPassword("password123")

# Start the listen/accept thread to begin accepting SOCKS proxy client connections.
# Listen on port 1080.
success = tunnel.BeginAccepting(1080)
if (success != true)
    print tunnel.lastErrorText() + "\n";
    exit
end

# 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 = Chilkat::CkFtp2.new()

# Indicate that the HTTP object is to use our portable SOCKS proxy/SSH tunnel running in our background thread.
ftp.put_SocksHostname("localhost")
# The SocksPort must equal the port passed to BeginAccepting above.
ftp.put_SocksPort(1080)
ftp.put_SocksVersion(5)
# The SOCKS5 login/password set here must equal the InboundSocksUsername/Password set above.
ftp.put_SocksUsername("chilkat123")
ftp.put_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.put_Hostname("ftp.someFtpServer.com")
ftp.put_Username("myLogin")
ftp.put_Password("myPassword")
ftp.put_AuthTls(true)

# Connect and login (via the SSH tunnel) to the FTP server.
success = ftp.Connect()
if (success != true)
    print ftp.lastErrorText() + "\n";
    exit
end

# 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 != true)
    print ftp.lastErrorText() + "\n";
    exit
end

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 != true)
    print ftp.lastErrorText() + "\n";
    exit
end

# 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 != true)
    print tunnel.lastErrorText() + "\n";
    exit
end

# Close the SSH tunnel (would also kick any remaining connected clients).
success = tunnel.CloseTunnel(waitForThreadExit)
if (success != true)
    print tunnel.lastErrorText() + "\n";
    exit
end