(Excel) 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.

Dim tunnel As Chilkat.Socket
Set tunnel = Chilkat.NewSocket


sshHostname = "sftp.example.com"

sshPort = 22

' Connect to an SSH server and establish the SSH tunnel:

success = tunnel.SshOpenTunnel(sshHostname,sshPort)
If (success <> True) Then
    Debug.Print tunnel.LastErrorText
    Exit Sub
End If

' Authenticate with the SSH server via a login/password
' or with a public key.
' This example demonstrates SSH password authentication.
success = tunnel.SshAuthenticatePw("mySshLogin","mySshPassword")
If (success <> True) Then
    Debug.Print tunnel.LastErrorText
    Exit Sub
End If

' 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


maxWaitMs = 4000

useTls = False
Set channel = tunnel.SshOpenChannel("time-c.nist.gov",37,useTls,maxWaitMs)
If (tunnel.LastMethodSuccess = False) Then
    Debug.Print tunnel.LastErrorText
    Exit Sub
End If

' 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
' True or False to indicate success.  If successful, the integer
' is obtained via the ReceivedInt property.

bigEndian = True
success = channel.ReceiveInt32(bigEndian)
If (success <> True) Then
    Debug.Print channel.LastErrorText

    Exit Sub
End If

Dim dt As Chilkat.CkDateTime
Set dt = Chilkat.NewCkDateTime
Dim success As Boolean
success = dt.SetFromNtpTime(channel.ReceivedInt)

' Show the current local date/time

bLocalTime = True
Debug.Print "Current local date/time: "; dt.GetAsRfc822(bLocalTime)

' Close the SSH channel.
success = channel.Close(maxWaitMs)
If (success <> True) Then
    Debug.Print channel.LastErrorText

    Exit Sub
End If

' 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.
Set channel = tunnel.SshOpenChannel("time-a.nist.gov",37,useTls,maxWaitMs)
If (tunnel.LastMethodSuccess = False) Then
    Debug.Print tunnel.LastErrorText
    Exit Sub
End If

' Review the LastErrorText to see that the connection was made via the SSH tunnel:
Debug.Print tunnel.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.
success = channel.Close(maxWaitMs)
If (success <> True) Then
    Debug.Print channel.LastErrorText

    Exit Sub
End If

' Finally, close the SSH tunnel.
success = tunnel.SshCloseTunnel()
If (success <> True) Then
    Debug.Print tunnel.LastErrorText
    Exit Sub
End If

Debug.Print "TCP SSH tunneling example completed."