DataFlex

Send and Receive WebSocket Messages

See more WebSocket Examples

This example how to send and receive websocket messages.

A WebSocket message can be composed of one or more frames. The simple case is where a single frame is both the first and last frame in a message. This is the case where the 1st frame in the message has the "final frame" bit set.

This example demonstrates sending and receiving multi-frame messages.

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.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoWs
    Variant vRest
    Handle hoRest
    String sResponseBodyIgnored
    Boolean iFinalFrame
    Boolean iReceivedFinalFrame
    String sReceivedMsg
    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(cComChilkatWebSocket)) To hoWs
    If (Not(IsComObjectCreated(hoWs))) Begin
        Send CreateComObject of hoWs
    End

    // 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 demonstrates sending and receiving a multi-frame message.

    // The websocket message will be composed of three text lines, each frame will contain a single line.

    // 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

    // 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 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.
    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
    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