(Lianja) 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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// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

loTunnel = createobject("CkSocket")

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

// Connect to an SSH server and establish the SSH tunnel:
llSuccess = loTunnel.SshOpenTunnel(lcSshHostname,lnSshPort)
if (llSuccess <> .T.) then
    ? loTunnel.LastErrorText
    release loTunnel
    return
endif

// Authenticate with the SSH server via a login/password
// or with a public key.
// This example demonstrates SSH password authentication.
llSuccess = loTunnel.SshAuthenticatePw("mySshLogin","mySshPassword")
if (llSuccess <> .T.) then
    ? loTunnel.LastErrorText
    release loTunnel
    return
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
llUseTls = .F.
loChannel = loTunnel.SshOpenChannel("time-c.nist.gov",37,llUseTls,lnMaxWaitMs)
if (loTunnel.LastMethodSuccess = .F.) then
    ? loTunnel.LastErrorText
    release loTunnel
    return
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
// .T. or .F. to indicate success.  If successful, the integer
// is obtained via the ReceivedInt property.
llBigEndian = .T.
llSuccess = loChannel.ReceiveInt32(llBigEndian)
if (llSuccess <> .T.) then
    ? loChannel.LastErrorText
    release loChannel
    release loTunnel
    return
endif

loDt = createobject("CkDateTime")
loDt.SetFromNtpTime(loChannel.ReceivedInt)

// Show the current local date/time
llBLocalTime = .T.
? "Current local date/time: " + loDt.GetAsRfc822(llBLocalTime)

// Close the SSH channel.
llSuccess = loChannel.Close(lnMaxWaitMs)
if (llSuccess <> .T.) then
    ? loChannel.LastErrorText
    release loChannel
    release loTunnel
    release loDt
    return
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,llUseTls,lnMaxWaitMs)
if (loTunnel.LastMethodSuccess = .F.) then
    ? loTunnel.LastErrorText
    release loTunnel
    release loDt
    return
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.
llSuccess = loChannel.Close(lnMaxWaitMs)
if (llSuccess <> .T.) then
    ? loChannel.LastErrorText
    release loChannel
    release loTunnel
    release loDt
    return
endif

release loChannel

// Finally, close the SSH tunnel.
llSuccess = loTunnel.SshCloseTunnel()
if (llSuccess <> .T.) then
    ? loTunnel.LastErrorText
    release loTunnel
    release loDt
    return
endif

? "TCP SSH tunneling example completed."


release loTunnel
release loDt