Lianja

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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llSuccess = .F.

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

loRest = createobject("CkRest")

// 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("CkUrl")
loUrl.ParseUrl("http://www.nytimes.com/pages/business/index.html")

llBAutoReconnect = .T.
llSuccess = loRest.Connect(loUrl.Host,loUrl.Port,loUrl.Ssl,llBAutoReconnect)

// Send the GET request (This sends the GET request, but does not read the response.)
llSuccess = loRest.SendReqNoBody("GET",loUrl.Path)
if (llSuccess <> .T.) then
    ? loRest.LastErrorText
    release loRest
    release loUrl
    return
endif

// Read the response header.
lnResponseStatusCode = loRest.ReadResponseHeader()
if (lnResponseStatusCode < 0) then
    ? loRest.LastErrorText
    release loRest
    release loUrl
    return
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 <> .T.) then
        ? loRest.LastErrorText
    else
        ? lcErrResponse
    endif

    release loRest
    release loUrl
    return
endif

loBodyStream = createobject("CkStream")
// 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,.T.)

// Start the task. 
llSuccess = loReadResponseBodyTask.Run()

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

loSbBody = createobject("CkStringBuilder")
llExitLoop = .F.
do while not llExitLoop and (loBodyStream.EndOfStream <> .T.)

    lcBodyText = loBodyStream.ReadString()
    if (loBodyStream.LastMethodSuccess = .T.) then
        loSbBody.Append(lcBodyText)
        if (loSbBody.Contains("</head>",.F.)) then
            llExitLoop = .T.
        endif

    else
        llExitLoop = .T.
    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