Visual FoxPro

TCP Socket through SSH Tunnel (Port Forwarding)

See more Socket/SSL/TLS Examples

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.

Visual FoxPro

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

lnSuccess = 0

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

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 = 0) 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 = 0) 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 = CreateObject('Chilkat.Socket')
lnSuccess = loTunnel.SshNewChannel("time-c.nist.gov",37,lnUseTls,lnMaxWaitMs,loChannel)
IF (lnSuccess = 0) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    RELEASE loChannel
    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 = 0) THEN
    ? loChannel.LastErrorText
    RELEASE loTunnel
    RELEASE loChannel
    CANCEL
ENDIF

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 loTunnel
    RELEASE loChannel
    RELEASE loDt
    CANCEL
ENDIF

* 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.
lnSuccess = loTunnel.SshNewChannel("time-a.nist.gov",37,lnUseTls,lnMaxWaitMs,loChannel)
IF (lnSuccess = 0) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    RELEASE loChannel
    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 loTunnel
    RELEASE loChannel
    RELEASE loDt
    CANCEL
ENDIF

* Finally, close the SSH tunnel.
lnSuccess = loTunnel.SshCloseTunnel()
IF (lnSuccess = 0) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    RELEASE loChannel
    RELEASE loDt
    CANCEL
ENDIF

? "TCP SSH tunneling example completed."

RELEASE loTunnel
RELEASE loChannel
RELEASE loDt