(DataFlex) HTTP GET -- Read Response from Stream

Demonstrates how to send an HTTP GET for a web page, and then read the response from a Stream. The purpose is to fulfill a situation such as the following: "I have a URL and just want the <head> </head> portion of the HTML. This would avoid having to download a potentially enormous web page just to get at header information, such as the <styles>."

Chilkat ActiveX Downloads

ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoRest
    Handle hoUrl
    Boolean iSuccess
    Boolean iBAutoReconnect
    Boolean iSuccess
    Integer iResponseStatusCode
    String sErrResponse
    Variant vBodyStream
    Handle hoBodyStream
    Variant vReadResponseBodyTask
    Handle hoReadResponseBodyTask
    Handle hoSbBody
    Boolean iExitLoop
    String sBodyText
    Integer iMaxWaitMs
    String sTemp1
    Integer iTemp1
    Boolean bTemp1

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

    Get Create (RefClass(cComChilkatRest)) To hoRest
    If (Not(IsComObjectCreated(hoRest))) Begin
        Send CreateComObject of hoRest
    End

    // In this example, we'll get the web page at http://www.nytimes.com/pages/business/index.html
    // The domain is "www.nytimes.com", and the path is "/pages/business/index.html"

    // If we have only the full URL to begin with, it can be loaded into the Chilkat URL object to
    // access the parts:
    Get Create (RefClass(cComChilkatUrl)) To hoUrl
    If (Not(IsComObjectCreated(hoUrl))) Begin
        Send CreateComObject of hoUrl
    End
    Get ComParseUrl Of hoUrl "http://www.nytimes.com/pages/business/index.html" To iSuccess

    Move True To iBAutoReconnect
    Get ComHost Of hoUrl To sTemp1
    Get ComPort Of hoUrl To iTemp1
    Get ComSsl Of hoUrl To bTemp1
    Get ComConnect Of hoRest sTemp1 iTemp1 bTemp1 iBAutoReconnect To iSuccess

    // Send the GET request (This sends the GET request, but does not read the response.)
    Get ComPath Of hoUrl To sTemp1
    Get ComSendReqNoBody Of hoRest "GET" sTemp1 To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoRest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Read the response header.
    Get ComReadResponseHeader Of hoRest To iResponseStatusCode
    If (iResponseStatusCode < 0) Begin
        Get ComLastErrorText Of hoRest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Showln "Response status code = " iResponseStatusCode

    // We expect a 200 response status.
    If (iResponseStatusCode <> 200) Begin

        // If the response status code is not 200, we could check for a redirect status code and 
        // then follow it, read the entire response (as shown here), or just call rest.Disconnect
        Get ComReadRespBodyString Of hoRest To sErrResponse
        Get ComLastMethodSuccess Of hoRest To bTemp1
        If (bTemp1 <> True) Begin
            Get ComLastErrorText Of hoRest To sTemp1
            Showln sTemp1
        End
        Else Begin
            Showln sErrResponse
        End

        Procedure_Return
    End

    Get Create (RefClass(cComChilkatStream)) To hoBodyStream
    If (Not(IsComObjectCreated(hoBodyStream))) Begin
        Send CreateComObject of hoBodyStream
    End
    // Set a 10 second read timeout for the stream. 
    // (Give up if no data arrives within 10 seconds after calling a read method.)
    Set ComReadTimeoutMs Of hoBodyStream To 10000

    // Create a background thread task to read the response body (which feeds
    // it to the bodyStream object.)
    Get pvComObject of hoBodyStream to vBodyStream
    Get ComReadRespBodyStreamAsync Of hoRest vBodyStream True To vReadResponseBodyTask
    If (IsComObject(vReadResponseBodyTask)) Begin
        Get Create (RefClass(cComChilkatTask)) To hoReadResponseBodyTask
        Set pvComObject Of hoReadResponseBodyTask To vReadResponseBodyTask
    End

    // Start the task. 
    Get ComRun Of hoReadResponseBodyTask To iSuccess

    // Read the HTTP response body until the "</head>" is seen, or until
    // the end-of-stream is reached.

    Get Create (RefClass(cComChilkatStringBuilder)) To hoSbBody
    If (Not(IsComObjectCreated(hoSbBody))) Begin
        Send CreateComObject of hoSbBody
    End
    Move False To iExitLoop
    While (Not iExitLoop And ((ComEndOfStream(hoBodyStream)) <> True))

        Get ComReadString Of hoBodyStream To sBodyText
        Get ComLastMethodSuccess Of hoBodyStream To bTemp1
        If (bTemp1 = True) Begin
            Get ComAppend Of hoSbBody sBodyText To iSuccess
            Get ComContains Of hoSbBody "</head>" False To bTemp1
            If (bTemp1) Begin
                Move True To iExitLoop
            End

        End
        Else Begin
            Move True To iExitLoop
        End

    Loop

    // Cancel the remainder of the task...
    Get ComCancel Of hoReadResponseBodyTask To iSuccess

    Send Destroy of hoReadResponseBodyTask

    // Ensure we're disconnected from the server.
    Move 50 To iMaxWaitMs
    Get ComDisconnect Of hoRest iMaxWaitMs To iSuccess

    Showln "----"
    Get ComGetAsString Of hoSbBody To sTemp1
    Showln sTemp1
    Showln "----"
    Showln "Successfully received the body up to the desired point."


End_Procedure