Xin chào các bạn, bài viết hôm nay mình tiếp tục hướng dẫn các bạn cách giải image captcha sử dụng dịch vụ AZCapcha trên lập trình VB.NET winform.

Bài viết chỉ nhằm mục đích học tập, cách gọi API, không sử dụng cho mục đích xấu truy cập website trái phép.

[VB.NET] Hướng dẫn giải captcha sử dụng dịch vụ AZCaptcha API trên winform


AZCaptcha là dịch vụ api giải captcha: Image Captcha (normal captcha), Hcaptcha, recaptcha v1, v2 of Google...

Dưới đây, là hình ảnh demo ứng dụng:

Đầu tiên, các bạn cần đăng ký 1 tài khoản API tại đường dẫn: https://azcaptcha.com/

Với tài khoản đăng ký bạn sẽ được request miễn phí 50 lần.

Còn phí thì chỉ có 0/4$ / 1000 captcha, và mua tối thiểu phải 10$ qua cổng thanh toán: paypal, visa...

Đầu tiên, mình đã tạo sẵn 1 class AZCaptchaHelper.vb, để gọi Api này.

Video hướng dẫn Step by step:
Source code AZCaptchaHelper.vb
Imports System.IO
Imports System.Net
Imports System.Text

Public Class AZCaptchaHelper

    Public Shared Function GetHTMLForm(ByVal Url As String) As String
        Dim myRequest As HttpWebRequest = CType(WebRequest.Create(Url), HttpWebRequest)
        myRequest.Method = "GET"
        Dim myResponse As WebResponse = myRequest.GetResponse()
        Dim sr As StreamReader = New StreamReader(myResponse.GetResponseStream(), System.Text.Encoding.UTF8)
        Dim result As String = sr.ReadToEnd()
        sr.Close()
        myResponse.Close()
        Return result
    End Function
    Public Shared Function ImageToBase64(img As Image) As String
        Return Convert.ToBase64String(ImageToByteArray(img))
    End Function
    Public Shared Function ImageToByteArray(img As Image) As Byte()
        Using strm As New MemoryStream
            img.Save(strm, img.RawFormat)
            Return strm.GetBuffer()
        End Using
    End Function
    Public Shared Function GetStringFromCaptcha(base64string As String, API_KEY As String) As String
        Try
            System.Net.ServicePointManager.Expect100Continue = False
            Dim request = CType(WebRequest.Create("http://azcaptcha.com/in.php"), HttpWebRequest)

            Dim postData = "method=base64&key=" & API_KEY & "&body=" + WebUtility.UrlEncode(base64string)
            Dim data = Encoding.ASCII.GetBytes(postData)
            request.Method = "POST"
            request.ContentType = "application/x-www-form-urlencoded"
            request.ContentLength = data.Length

            Using stream = request.GetRequestStream()
                stream.Write(data, 0, data.Length)
            End Using

            Dim response = CType(request.GetResponse(), HttpWebResponse)
            Dim responseString As String = New StreamReader(response.GetResponseStream()).ReadToEnd()

            If responseString.Contains("OK|") Then
                Dim captcha As String = ""

                While True
                    captcha = GetHTMLForm("http://azcaptcha.com/res.php?key=" & API_KEY & "&action=get&id=" & responseString.Split("|"c)(1))

                    If captcha = "CAPCHA_NOT_READY" Then
                        System.Threading.Thread.Sleep(500)
                        Continue While
                    End If

                    If captcha = "_" Then
                        System.Threading.Thread.Sleep(500)
                        Continue While
                    End If

                    If captcha.Contains("OK|") Then
                        captcha = captcha.Replace("OK|", "")
                    End If

                    Return captcha
                End While
            End If

            Return ""
        Catch e As Exception
            Dim tt As String = e.Message
            Return tt
        End Try
    End Function
End Class

Và cách gọi sử dụng ở form1.vb
Imports System.IO
Imports System.Net
Imports System.Text

Public Class AZCaptchaHelper

    Public Shared Function GetHTMLForm(ByVal Url As String) As String
        Dim myRequest As HttpWebRequest = CType(WebRequest.Create(Url), HttpWebRequest)
        myRequest.Method = "GET"
        Dim myResponse As WebResponse = myRequest.GetResponse()
        Dim sr As StreamReader = New StreamReader(myResponse.GetResponseStream(), System.Text.Encoding.UTF8)
        Dim result As String = sr.ReadToEnd()
        sr.Close()
        myResponse.Close()
        Return result
    End Function
    Public Shared Function ImageToBase64(img As Image) As String
        Return Convert.ToBase64String(ImageToByteArray(img))
    End Function
    Public Shared Function ImageToByteArray(img As Image) As Byte()
        Using strm As New MemoryStream
            img.Save(strm, img.RawFormat)
            Return strm.GetBuffer()
        End Using
    End Function
    Public Shared Function GetStringFromCaptcha(base64string As String, API_KEY As String) As String
        Try
            System.Net.ServicePointManager.Expect100Continue = False
            Dim request = CType(WebRequest.Create("http://azcaptcha.com/in.php"), HttpWebRequest)

            Dim postData = "method=base64&key=" & API_KEY & "&body=" + WebUtility.UrlEncode(base64string)
            Dim data = Encoding.ASCII.GetBytes(postData)
            request.Method = "POST"
            request.ContentType = "application/x-www-form-urlencoded"
            request.ContentLength = data.Length

            Using stream = request.GetRequestStream()
                stream.Write(data, 0, data.Length)
            End Using

            Dim response = CType(request.GetResponse(), HttpWebResponse)
            Dim responseString As String = New StreamReader(response.GetResponseStream()).ReadToEnd()

            If responseString.Contains("OK|") Then
                Dim captcha As String = ""

                While True
                    captcha = GetHTMLForm("http://azcaptcha.com/res.php?key=" & API_KEY & "&action=get&id=" & responseString.Split("|"c)(1))

                    If captcha = "CAPCHA_NOT_READY" Then
                        System.Threading.Thread.Sleep(500)
                        Continue While
                    End If

                    If captcha = "_" Then
                        System.Threading.Thread.Sleep(500)
                        Continue While
                    End If

                    If captcha.Contains("OK|") Then
                        captcha = captcha.Replace("OK|", "")
                    End If

                    Return captcha
                End While
            End If

            Return ""
        Catch e As Exception
            Dim tt As String = e.Message
            Return tt
        End Try
    End Function
End Class

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