Visual Basic 6.0

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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Visual Basic 6.0

Dim success As Long
success = 0

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

Dim rest As New ChilkatRest

' 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:
Dim url As New ChilkatUrl
success = url.ParseUrl("http://www.nytimes.com/pages/business/index.html")

Dim bAutoReconnect As Long
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
    Debug.Print rest.LastErrorText
    Exit Sub
End If

' Read the response header.
Dim responseStatusCode As Long
responseStatusCode = rest.ReadResponseHeader()
If (responseStatusCode < 0) Then
    Debug.Print rest.LastErrorText
    Exit Sub
End If

Debug.Print "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
    Dim errResponse As String
    errResponse = rest.ReadRespBodyString()
    If (rest.LastMethodSuccess <> 1) Then
        Debug.Print rest.LastErrorText
    Else
        Debug.Print errResponse
    End If

    Exit Sub
End If

Dim bodyStream As New ChilkatStream
' 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.)
Dim readResponseBodyTask As ChilkatTask
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.

Dim sbBody As New ChilkatStringBuilder
Dim exitLoop As Long
exitLoop = 0
Do While Not exitLoop And (bodyStream.EndOfStream <> 1)

    Dim bodyText As String
    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.
Dim maxWaitMs As Long
maxWaitMs = 50
success = rest.Disconnect(maxWaitMs)

Debug.Print "----"
Debug.Print sbBody.GetAsString()
Debug.Print "----"
Debug.Print "Successfully received the body up to the desired point."