Visual FoxPro

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>."

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LOCAL lnSuccess
LOCAL loRest
LOCAL loUrl
LOCAL lnBAutoReconnect
LOCAL lnResponseStatusCode
LOCAL lcErrResponse
LOCAL loBodyStream
LOCAL loReadResponseBodyTask
LOCAL loSbBody
LOCAL lnExitLoop
LOCAL lcBodyText
LOCAL lnMaxWaitMs

lnSuccess = 0

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

loRest = CreateObject('Chilkat.Rest')

* 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:
loUrl = CreateObject('Chilkat.Url')
loUrl.ParseUrl("http://www.nytimes.com/pages/business/index.html")

lnBAutoReconnect = 1
lnSuccess = loRest.Connect(loUrl.Host,loUrl.Port,loUrl.Ssl,lnBAutoReconnect)

* Send the GET request (This sends the GET request, but does not read the response.)
lnSuccess = loRest.SendReqNoBody("GET",loUrl.Path)
IF (lnSuccess <> 1) THEN
    ? loRest.LastErrorText
    RELEASE loRest
    RELEASE loUrl
    CANCEL
ENDIF

* Read the response header.
lnResponseStatusCode = loRest.ReadResponseHeader()
IF (lnResponseStatusCode < 0) THEN
    ? loRest.LastErrorText
    RELEASE loRest
    RELEASE loUrl
    CANCEL
ENDIF

? "Response status code = " + STR(lnResponseStatusCode)

* We expect a 200 response status.
IF (lnResponseStatusCode <> 200) THEN

    * 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
    lcErrResponse = loRest.ReadRespBodyString()
    IF (loRest.LastMethodSuccess <> 1) THEN
        ? loRest.LastErrorText
    ELSE
        ? lcErrResponse
    ENDIF

    RELEASE loRest
    RELEASE loUrl
    CANCEL
ENDIF

loBodyStream = CreateObject('Chilkat.Stream')
* Set a 10 second read timeout for the stream. 
* (Give up if no data arrives within 10 seconds after calling a read method.)
loBodyStream.ReadTimeoutMs = 10000

* Create a background thread task to read the response body (which feeds
* it to the bodyStream object.)
loReadResponseBodyTask = loRest.ReadRespBodyStreamAsync(loBodyStream,1)

* Start the task. 
lnSuccess = loReadResponseBodyTask.Run()

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

loSbBody = CreateObject('Chilkat.StringBuilder')
lnExitLoop = 0
DO WHILE NOT lnExitLoop AND (loBodyStream.EndOfStream <> 1)

    lcBodyText = loBodyStream.ReadString()
    IF (loBodyStream.LastMethodSuccess = 1) THEN
        loSbBody.Append(lcBodyText)
        IF (loSbBody.Contains("</head>",0)) THEN
            lnExitLoop = 1
        ENDIF

    ELSE
        lnExitLoop = 1
    ENDIF

ENDDO

* Cancel the remainder of the task...
loReadResponseBodyTask.Cancel()

RELEASE loReadResponseBodyTask

* Ensure we're disconnected from the server.
lnMaxWaitMs = 50
loRest.Disconnect(lnMaxWaitMs)

? "----"
? loSbBody.GetAsString()
? "----"
? "Successfully received the body up to the desired point."

RELEASE loRest
RELEASE loUrl
RELEASE loBodyStream
RELEASE loSbBody