Xbase++

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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LOCAL nSuccess
LOCAL oSsh
LOCAL nSshPort
LOCAL cPassword
LOCAL cTargetHostname
LOCAL nTargetPort
LOCAL nChannelNum

nSuccess := 0

//  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.

oSsh := CreateObject("Chilkat.Ssh")

nSshPort := 22
nSuccess := oSsh:Connect("ssh.example.com", nSshPort)
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

//  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.
cPassword := "mySshPassword"

nSuccess := oSsh:AuthenticatePw("mySshLogin", cPassword)
IF (nSuccess == 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

//  The target name is resolved by the SSH server, not by this computer, so it must be
//  reachable from the server's network.
cTargetHostname := "db.internal.example.com"
nTargetPort := 5432
nChannelNum := oSsh:OpenDirectTcpIpChannel(cTargetHostname, nTargetPort)
IF (nChannelNum < 0)
    ? oSsh:LastErrorText
    oSsh:destroy()
    RETURN
ENDIF

? "Opened direct-tcpip channel: " + Str(nChannelNum)

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

oSsh:Disconnect()

oSsh:destroy()