Lua

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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Lua

local chilkat = require("chilkat")

-- 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.

local ssh = chilkat.Ssh.new()

local sshPort = 22
local success = ssh:connect("ssh.example.com", sshPort)
if not success then
    print(ssh.last_error_text)
    return
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.
local password = "mySshPassword"

success = ssh:authenticate_pw("mySshLogin", password)
if not success then
    print(ssh.last_error_text)
    return
end

-- The target name is resolved by the SSH server, not by this computer, so it must be
-- reachable from the server's network.
local targetHostname = "db.internal.example.com"
local targetPort = 5432
local channelNum = ssh:open_direct_tcp_ip_channel(targetHostname, targetPort)
if channelNum < 0 then
    print(ssh.last_error_text)
    return
end

print("Opened direct-tcpip channel: " .. channelNum)

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

ssh:disconnect()