CkPython

Open a direct-tcpip Channel (SSH Port Forwarding)

Demonstrates the Chilkat Ssh.OpenDirectTcpIpChannel method, which opens a direct-tcpip channel through the SSH server to a target host and port. The first argument is the target hostname and the second is the target port. It returns the channel number, or -1 on failure.

Background: This is SSH local port forwarding at the API level: the channel carries ordinary TCP traffic to a service that may be reachable only from the SSH server's network — a database, an internal web app, a message broker. The key detail is that the server resolves the target name, not your machine, so it must resolve and be reachable there. Supplying a numeric IPv4 address avoids remote DNS resolution entirely.

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import sys
import chilkat

success = False

#  Demonstrates the Ssh.OpenDirectTcpIpChannel method, which opens a direct-tcpip channel
#  through the SSH server to a target host and port.  The 1st argument is the target hostname
#  and the 2nd is the target port.  It returns the channel number, or -1 on failure.

ssh = chilkat.CkSsh()

sshPort = 22
success = ssh.Connect("ssh.example.com",sshPort)
if (success == False):
    print(ssh.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 = ssh.AuthenticatePw("mySshLogin",password)
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

#  The target name is resolved by the SSH server, not by this computer, so it must be
#  reachable from the server's network.
targetHostname = "db.internal.example.com"
targetPort = 5432
channelNum = ssh.OpenDirectTcpIpChannel(targetHostname,targetPort)
if (channelNum < 0):
    print(ssh.lastErrorText())
    sys.exit()

print("Opened direct-tcpip channel: " + str(channelNum))

#  The channel now carries ordinary TCP data to the target, tunneled over SSH.

ssh.Disconnect()