Chilkat2-Python

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.

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import sys
import chilkat2

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 = chilkat2.SshTunnel()

# The fixed destination that accepted connections are forwarded to.
tunnel.DestHostname = "db.internal.example.com"
tunnel.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.ListenBindIpAddress = "127.0.0.1"

sshPort = 22
success = tunnel.Connect("ssh.example.com",sshPort)
if (success == False):
    print(tunnel.LastErrorText)
    sys.exit()

# 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)
    sys.exit()

# 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)
    sys.exit()

print("Listening on 127.0.0.1 port " + str(tunnel.ListenPort))

# 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)
    sys.exit()