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(Visual Basic 6.0) 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.
' This example requires the Chilkat API to have been previously unlocked. ' See Global Unlock Sample for sample code. Dim tunnel As New ChilkatSocket Dim sshHostname As String sshHostname = "sftp.example.com" Dim sshPort As Long sshPort = 22 ' Connect to an SSH server and establish the SSH tunnel: Dim success As Long success = tunnel.SshOpenTunnel(sshHostname,sshPort) If (success <> 1) 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 <> 1) 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 Dim channel As ChilkatSocket Dim maxWaitMs As Long maxWaitMs = 4000 Dim useTls As Long useTls = 0 Set channel = tunnel.SshOpenChannel("time-c.nist.gov",37,useTls,maxWaitMs) If (tunnel.LastMethodSuccess = 0) 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 ' 1 or 0 to indicate success. If successful, the integer ' is obtained via the ReceivedInt property. Dim bigEndian As Long bigEndian = 1 success = channel.ReceiveInt32(bigEndian) If (success <> 1) Then Debug.Print channel.LastErrorText Exit Sub End If Dim dt As New CkDateTime success = dt.SetFromNtpTime(channel.ReceivedInt) ' Show the current local date/time Dim bLocalTime As Long bLocalTime = 1 Debug.Print "Current local date/time: " & dt.GetAsRfc822(bLocalTime) ' Close the SSH channel. success = channel.Close(maxWaitMs) If (success <> 1) 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 = 0) 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 <> 1) Then Debug.Print channel.LastErrorText Exit Sub End If ' Finally, close the SSH tunnel. success = tunnel.SshCloseTunnel() If (success <> 1) Then Debug.Print tunnel.LastErrorText Exit Sub End If Debug.Print "TCP SSH tunneling example completed."
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