Ruby

SSH Tunnel Static (Fixed-Destination) Port Forwarding

Demonstrates fixed-destination port forwarding with the DestHostname, DestPort, ListenBindIpAddress, and ListenPort properties. Every local connection accepted by the listener is forwarded to the same fixed destination through the SSH server.

Background: This is the classic ssh -L scenario: expose a single remote service — a database, an internal web app — at a local port. Binding the listener to 127.0.0.1 keeps the tunnel private to the local machine, whereas 0.0.0.0 would let other hosts route through it. Passing 0 to BeginAccepting lets the OS pick a free port, which ListenPort then reports — handy when a fixed port might already be in use.

Chilkat Ruby Downloads

Download Chilkat for Ruby

Ruby

require 'chilkat'

success = false

#  Demonstrates fixed-destination (static) port forwarding with the SshTunnel properties
#  DestHostname, DestPort, ListenBindIpAddress, and ListenPort.
#  
#  Every local connection accepted by the listener is forwarded to the same fixed destination
#  through the SSH server.

tunnel = Chilkat::CkSshTunnel.new()

#  The fixed destination that accepted connections are forwarded to.
tunnel.put_DestHostname("db.internal.example.com")
tunnel.put_DestPort(5432)

#  Bind the listener to loopback so only local processes can use the tunnel.  Use "0.0.0.0" to
#  accept connections from other machines (less secure).
tunnel.put_ListenBindIpAddress("127.0.0.1")

sshPort = 22
success = tunnel.Connect("ssh.example.com",sshPort)
if (success == false)
    print tunnel.lastErrorText() + "\n";
    exit
end

#  Normally you would not hard-code the password in source.  You should instead obtain it
#  from an interactive prompt, environment variable, or a secrets vault.
password = "mySshPassword"

success = tunnel.AuthenticatePw("mySshLogin",password)
if (success == false)
    print tunnel.lastErrorText() + "\n";
    exit
end

#  Pass 0 to let the operating system choose an available port.  After BeginAccepting succeeds,
#  ListenPort contains the actual port that was bound.
success = tunnel.BeginAccepting(0)
if (success == false)
    print tunnel.lastErrorText() + "\n";
    exit
end

print "Listening on 127.0.0.1 port " + tunnel.get_ListenPort().to_s() + "\n";

#  Applications now connect to 127.0.0.1:ListenPort as if it were the database server.

waitForThreadExit = true
success = tunnel.CloseTunnel(waitForThreadExit)
if (success == false)
    print tunnel.lastErrorText() + "\n";
    exit
end