(Visual FoxPro) TCP Socket through SSH Tunnel (Port Forwarding)

Demonstrates using Chilkat Socket to communicate to a TCP service through an SSH tunnel. This example will connect to an NIST time server and (using the old Time Protocol (RFC 868)), will read the current GMT time.

Note: This is not necessarily a recommended means for getting the current date/time. The most commonly used time protocol is the Network Time Protocol (RFC-1305). The intent of this example is to show how TCP communications can occur through an SSH tunnel.

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LOCAL loTunnel
LOCAL lcSshHostname
LOCAL lnSshPort
LOCAL lnSuccess
LOCAL loChannel
LOCAL lnMaxWaitMs
LOCAL lnUseTls
LOCAL lnBigEndian
LOCAL loDt
LOCAL lnBLocalTime

* This example requires the Chilkat API to have been previously unlocked.
* See Global Unlock Sample for sample code.

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Socket')
loTunnel = CreateObject('Chilkat.Socket')

lcSshHostname = "sftp.example.com"
lnSshPort = 22

* Connect to an SSH server and establish the SSH tunnel:
lnSuccess = loTunnel.SshOpenTunnel(lcSshHostname,lnSshPort)
IF (lnSuccess <> 1) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    CANCEL
ENDIF

* Authenticate with the SSH server via a login/password
* or with a public key.
* This example demonstrates SSH password authentication.
lnSuccess = loTunnel.SshAuthenticatePw("mySshLogin","mySshPassword")
IF (lnSuccess <> 1) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    CANCEL
ENDIF

* OK, the SSH tunnel is setup.  Now open a channel within the tunnel.
* Once the channel is obtained, the Socket API may
* be used exactly the same as usual, except all communications
* are sent through the channel in the SSH tunnel.
* Any number of channels may be created from the same SSH tunnel.
* Multiple channels may coexist at the same time.

* Connect to an NIST time server and read the current date/time

lnMaxWaitMs = 4000
lnUseTls = 0
loChannel = loTunnel.SshOpenChannel("time-c.nist.gov",37,lnUseTls,lnMaxWaitMs)
IF (loTunnel.LastMethodSuccess = 0) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    CANCEL
ENDIF

* The time server will send a big-endian 32-bit integer representing
* the number of seconds since since 00:00 (midnight) 1 January 1900 GMT.
* The ReceiveInt32 method will receive a 4-byte integer, but returns
* 1 or 0 to indicate success.  If successful, the integer
* is obtained via the ReceivedInt property.
lnBigEndian = 1
lnSuccess = loChannel.ReceiveInt32(lnBigEndian)
IF (lnSuccess <> 1) THEN
    ? loChannel.LastErrorText
    RELEASE loChannel
    RELEASE loTunnel
    CANCEL
ENDIF

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.CkDateTime')
loDt = CreateObject('Chilkat.CkDateTime')
loDt.SetFromNtpTime(loChannel.ReceivedInt)

* Show the current local date/time
lnBLocalTime = 1
? "Current local date/time: " + loDt.GetAsRfc822(lnBLocalTime)

* Close the SSH channel.
lnSuccess = loChannel.Close(lnMaxWaitMs)
IF (lnSuccess <> 1) THEN
    ? loChannel.LastErrorText
    RELEASE loChannel
    RELEASE loTunnel
    RELEASE loDt
    CANCEL
ENDIF

RELEASE loChannel

* It is possible to create a new channel from the existing SSH tunnel for the next connection:
* Any number of channels may be created from the same SSH tunnel.
* Multiple channels may coexist at the same time.
loChannel = loTunnel.SshOpenChannel("time-a.nist.gov",37,lnUseTls,lnMaxWaitMs)
IF (loTunnel.LastMethodSuccess = 0) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    RELEASE loDt
    CANCEL
ENDIF

* Review the LastErrorText to see that the connection was made via the SSH tunnel:
? loTunnel.LastErrorText

* Close the connection to time-a.nist.gov.  This is actually closing our channel
* within the SSH tunnel, but keeps the tunnel open for the next port-forwarded connection.
lnSuccess = loChannel.Close(lnMaxWaitMs)
IF (lnSuccess <> 1) THEN
    ? loChannel.LastErrorText
    RELEASE loChannel
    RELEASE loTunnel
    RELEASE loDt
    CANCEL
ENDIF

RELEASE loChannel

* Finally, close the SSH tunnel.
lnSuccess = loTunnel.SshCloseTunnel()
IF (lnSuccess <> 1) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    RELEASE loDt
    CANCEL
ENDIF

? "TCP SSH tunneling example completed."

RELEASE loTunnel
RELEASE loDt