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DataFlex Examples

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(DataFlex) Send a WebSocket Ping Control Frame

Ping and Pong messages are the heartbeat of websockets. See Pings and Pongs

"At any point after the handshake, either the client or the server can choose to send a ping to the other party. When the ping is received, the recipient must send back a pong as soon as possible. You can use this to make sure that the client is still connected, for example. A ping or pong is just a regular frame, but it's a control frame. Pings have an opcode of 0x9, and pongs have an opcode of 0xA. When you get a ping, send back a pong with the exact same Payload Data as the ping (for pings and pongs, the max payload length is 125). You might also get a pong without ever sending a ping; ignore this if it happens."

This example demonstrates how to send a Ping in the midst of sending a message.

Note: The websockets.chilkat.io server imposes the following limitations:
Messages must be 16K or less, and each connection is limited to a max of 16 echoed messages.

Chilkat ActiveX Downloads

ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-9.5.0-win32.pkg

Procedure Test
    Handle hoWs
    Variant vRest
    Handle hoRest
    Boolean iSuccess
    String sResponseBodyIgnored
    Boolean iFinalFrame
    Boolean iReceivedFinalFrame
    String sReceivedMsg
    String sTemp1
    Integer iTemp1

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

    Get Create (RefClass(cComChilkatWebSocket)) To hoWs
    If (Not(IsComObjectCreated(hoWs))) Begin
        Send CreateComObject of hoWs
    End

    // The PongAutoConsume property is True by default.  This means that any Pong frames that are received 
    // will automatically be consumed, and the ReadFrame method will continue reading the next incoming frame before it returns.
    Set ComPongAutoConsume Of hoWs To True

    // For brevity, this example does not check for errors when etablishing the WebSocket connection.
    // See Establish WebSocket Connection for more complete sample code for making the connection.

    Get Create (RefClass(cComChilkatRest)) To hoRest
    If (Not(IsComObjectCreated(hoRest))) Begin
        Send CreateComObject of hoRest
    End
    // Connect to websockets.chilkat.io
    // IMPORTANT: websockets.chilkat.io accepts frames of up to 16K in size and echoes them back.
    // IMPORTANT: The websockets.chilkat.io server imposes the following limitations: 
    // ---------- Messages must be 16K or less, and each connection is limited to a max of 16 echoed messages.
    Get ComConnect Of hoRest "websockets.chilkat.io" 80 False False To iSuccess
    Get pvComObject of hoRest to vRest
    Get ComUseConnection Of hoWs vRest To iSuccess
    Get ComAddClientHeaders Of hoWs To iSuccess
    Get ComFullRequestNoBody Of hoRest "GET" "/wsChilkatEcho.ashx" To sResponseBodyIgnored
    Get ComValidateServerHandshake Of hoWs To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoWs To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // This example sends a multi-frame message to the Chilkat echo server, and reads the response.
    // In the midst of sending the message, we'll send a Ping control frame.  The server should respond with a Pong frame,
    // and we'll automatically consume it.

    // Send the 1st frame in the message.
    Move False To iFinalFrame
    Get ComSendFrame Of hoWs "This is the 1st frame" + (character(13)) + (character(10)) iFinalFrame To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoWs To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Let's send a Ping frame here...
    Get ComSendPing Of hoWs "This is a ping" To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoWs To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Send the 2nd frame in the message.
    Get ComSendFrame Of hoWs "This is the 2nd frame" + (character(13)) + (character(10)) iFinalFrame To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoWs To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Send the 3rd and final frame in the message.
    Move True To iFinalFrame
    Get ComSendFrame Of hoWs "This is the 3rd and final frame" + (character(13)) + (character(10)) iFinalFrame To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoWs To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Read an incoming frames until we receive the final frame.
    // Note: It may be that the echo server (websockets.chilkat.io) responds with 
    // the full message in a single final frame.
    // 
    // The Pong response will be consumed automatically because the PongAutoConsume property is True.
    // Therefore, we don't need to worry about handling an incoming Pong.
    Move False To iReceivedFinalFrame
    While (iReceivedFinalFrame = False)

        Get ComReadFrame Of hoWs To iSuccess
        If (iSuccess <> True) Begin
            Showln "Failed to receive a frame"
            Get ComReadFrameFailReason Of hoWs To iTemp1
            Showln "ReadFrame fail reason = " iTemp1
            Get ComLastErrorText Of hoWs To sTemp1
            Showln sTemp1
            Procedure_Return
        End

        Get ComFinalFrame Of hoWs To iReceivedFinalFrame

        // Show the opcode and final frame bit for the frame just received:
        Get ComFrameOpcode Of hoWs To sTemp1
        Showln "Frame opcode: " sTemp1
        Showln "Final frame: " iReceivedFinalFrame
        Showln "--"
    Loop

    // Return the message accumulated in the above calls to ReadFrame.
    Get ComGetFrameData Of hoWs To sReceivedMsg
    Showln "Received: " sReceivedMsg

    // Close the websocket connection.
    Get ComSendClose Of hoWs True 1000 "Closing this websocket." To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoWs To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Read the Close response.
    Get ComReadFrame Of hoWs To iSuccess
    If (iSuccess <> True) Begin
        Get ComReadFrameFailReason Of hoWs To iTemp1
        Showln "ReadFrame fail reason = " iTemp1
        Get ComLastErrorText Of hoWs To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Should receive the "Close" opcode.
    Get ComFrameOpcode Of hoWs To sTemp1
    Showln "Received opcode: " sTemp1
    // Should be the same status code we sent (1000)
    Get ComCloseStatusCode Of hoWs To iTemp1
    Showln "Received close status code: " iTemp1
    // The server may echo the close reason.  If not, this will be empty.
    Get ComCloseReason Of hoWs To sTemp1
    Showln "Echoed close reason: " sTemp1

    Showln "Success."


End_Procedure

 

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