DataFlex

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.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoTunnel
    String sSshHostname
    Integer iSshPort
    Integer iMaxWaitMs
    Boolean iUseTls
    Variant vChannel
    Handle hoChannel
    Boolean iBigEndian
    Handle hoDt
    Boolean iBLocalTime
    String sTemp1
    Integer iTemp1

    Move False To iSuccess

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

    Get Create (RefClass(cComChilkatSocket)) To hoTunnel
    If (Not(IsComObjectCreated(hoTunnel))) Begin
        Send CreateComObject of hoTunnel
    End

    Move "sftp.example.com" To sSshHostname
    Move 22 To iSshPort

    // Connect to an SSH server and establish the SSH tunnel:
    Get ComSshOpenTunnel Of hoTunnel sSshHostname iSshPort To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Authenticate with the SSH server via a login/password
    // or with a public key.
    // This example demonstrates SSH password authentication.
    Get ComSshAuthenticatePw Of hoTunnel "mySshLogin" "mySshPassword" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // 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
    Move 4000 To iMaxWaitMs
    Move False To iUseTls
    Get Create (RefClass(cComChilkatSocket)) To hoChannel
    If (Not(IsComObjectCreated(hoChannel))) Begin
        Send CreateComObject of hoChannel
    End
    Get pvComObject of hoChannel to vChannel
    Get ComSshNewChannel Of hoTunnel "time-c.nist.gov" 37 iUseTls iMaxWaitMs vChannel To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // 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.
    Move True To iBigEndian
    Get ComReceiveInt32 Of hoChannel iBigEndian To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoChannel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get Create (RefClass(cComCkDateTime)) To hoDt
    If (Not(IsComObjectCreated(hoDt))) Begin
        Send CreateComObject of hoDt
    End
    Get ComReceivedInt Of hoChannel To iTemp1
    Get ComSetFromNtpTime Of hoDt iTemp1 To iSuccess

    // Show the current local date/time
    Move True To iBLocalTime
    Get ComGetAsRfc822 Of hoDt iBLocalTime To sTemp1
    Showln "Current local date/time: " sTemp1

    // Close the SSH channel.
    Get ComClose Of hoChannel iMaxWaitMs To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoChannel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // 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.
    Get pvComObject of hoChannel to vChannel
    Get ComSshNewChannel Of hoTunnel "time-a.nist.gov" 37 iUseTls iMaxWaitMs vChannel To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Review the LastErrorText to see that the connection was made via the SSH tunnel:
    Get ComLastErrorText Of hoTunnel To sTemp1
    Showln sTemp1

    // 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.
    Get ComClose Of hoChannel iMaxWaitMs To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoChannel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Finally, close the SSH tunnel.
    Get ComSshCloseTunnel Of hoTunnel To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Showln "TCP SSH tunneling example completed."


End_Procedure