VBScript

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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Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
'Create a Unicode (utf-16) output text file.
Set outFile = fso.CreateTextFile("output.txt", True, True)

success = 0

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

set rest = 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:
set url = CreateObject("Chilkat.Url")
success = url.ParseUrl("http://www.nytimes.com/pages/business/index.html")

bAutoReconnect = 1
success = rest.Connect(url.Host,url.Port,url.Ssl,bAutoReconnect)

' Send the GET request (This sends the GET request, but does not read the response.)
success = rest.SendReqNoBody("GET",url.Path)
If (success <> 1) Then
    outFile.WriteLine(rest.LastErrorText)
    WScript.Quit
End If

' Read the response header.
responseStatusCode = rest.ReadResponseHeader()
If (responseStatusCode < 0) Then
    outFile.WriteLine(rest.LastErrorText)
    WScript.Quit
End If

outFile.WriteLine("Response status code = " & responseStatusCode)

' We expect a 200 response status.
If (responseStatusCode <> 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
    errResponse = rest.ReadRespBodyString()
    If (rest.LastMethodSuccess <> 1) Then
        outFile.WriteLine(rest.LastErrorText)
    Else
        outFile.WriteLine(errResponse)
    End If

    WScript.Quit
End If

set bodyStream = 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.)
bodyStream.ReadTimeoutMs = 10000

' Create a background thread task to read the response body (which feeds
' it to the bodyStream object.)
' readResponseBodyTask is a Chilkat.Task
Set readResponseBodyTask = rest.ReadRespBodyStreamAsync(bodyStream,1)

' Start the task. 
success = readResponseBodyTask.Run()

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

set sbBody = CreateObject("Chilkat.StringBuilder")
exitLoop = 0
Do While Not exitLoop And (bodyStream.EndOfStream <> 1)

    bodyText = bodyStream.ReadString()
    If (bodyStream.LastMethodSuccess = 1) Then
        success = sbBody.Append(bodyText)
        If (sbBody.Contains("</head>",0)) Then
            exitLoop = 1
        End If

    Else
        exitLoop = 1
    End If

Loop

' Cancel the remainder of the task...
success = readResponseBodyTask.Cancel()

' Ensure we're disconnected from the server.
maxWaitMs = 50
success = rest.Disconnect(maxWaitMs)

outFile.WriteLine("----")
outFile.WriteLine(sbBody.GetAsString())
outFile.WriteLine("----")
outFile.WriteLine("Successfully received the body up to the desired point.")

outFile.Close