DataFlex

SSH Tunnel TCP Socket Options

Demonstrates tuning the underlying TCP socket with the SoRcvBuf, SoSndBuf, TcpNoDelay, OutboundBindIpAddress, and OutboundBindPort properties. These normally should be left at their defaults.

Background: These are low-level knobs for specific situations. Larger send/receive buffers can improve throughput on high-bandwidth, high-latency ("long fat") links; TcpNoDelay disables Nagle's algorithm to cut latency for small interactive packets at the cost of efficiency; and binding the outbound socket to a specific local address or port is occasionally required by firewall rules or multi-homed hosts. Change them only with a concrete reason, since the defaults are tuned for the common case.

Chilkat DataFlex Downloads

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DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoTunnel
    Integer iSshPort
    String sPassword
    Integer iListenPort
    Boolean iWaitForThreadExit
    String sTemp1

    Move False To iSuccess

    //  Demonstrates tuning the underlying TCP socket with the SshTunnel properties SoRcvBuf, SoSndBuf,
    //  TcpNoDelay, OutboundBindIpAddress, and OutboundBindPort.
    //  
    //  These normally should be left at their defaults; adjust them only for specific performance or
    //  networking requirements.

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

    //  Socket send/receive buffer sizes, in bytes.  Larger buffers can help throughput on
    //  high-latency links.
    Set ComSoRcvBuf Of hoTunnel To 4194304
    Set ComSoSndBuf Of hoTunnel To 262144

    //  Disable Nagle's algorithm to reduce latency for small, interactive packets.
    Set ComTcpNoDelay Of hoTunnel To True

    //  Bind the outbound socket to a specific local address/port before connecting.  0 (the default)
    //  lets the OS choose the local port; an empty address lets the OS choose the interface.
    Set ComOutboundBindIpAddress Of hoTunnel To "192.168.1.50"
    Set ComOutboundBindPort Of hoTunnel To 0

    Set ComDestHostname Of hoTunnel To "db.internal.example.com"
    Set ComDestPort Of hoTunnel To 5432

    Move 22 To iSshPort
    Get ComConnect Of hoTunnel "ssh.example.com" iSshPort To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  Normally you would not hard-code the password in source.  You should instead obtain it
    //  from an interactive prompt, environment variable, or a secrets vault.
    Move "mySshPassword" To sPassword

    Get ComAuthenticatePw Of hoTunnel "mySshLogin" sPassword To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Move 1080 To iListenPort
    Get ComBeginAccepting Of hoTunnel iListenPort To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Showln "Tunnel established with custom socket options."

    Move True To iWaitForThreadExit
    Get ComCloseTunnel Of hoTunnel iWaitForThreadExit To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End



End_Procedure