vb.net multiple webproxy in httpwebrequest - asp.net

Question

I am currently working on a VB.net project where I need to get http responses from a certain URI but the requests needs to go through http proxy which I am perfectly fine with. The problem occurred when I realised sometimes our proxy servers are not working and then the application throws an error. I want my app to check whether the proxy is working or not, if not then I want it to take another proxy from the proxy list/array. And also, please feel free to share if you have any alternative ideas.
Currently I am using this (which is static and when it throws an error I need to manually change the proxy):
Dim proxyObject As WebProxy = New WebProxy("192.168.0.10:80")
request.Proxy = proxyObject
What I want is something like this:
If WebProxy("192.168.0.10:80") is working fine Then
Execute the response
Else
Take the next proxy address from the list/array and go back to the starting
of "If"
End If
FYI: my proxies doesn't require authentication.
I apologise if I couldn't explain it properly and to be honest I'm fairly new in VB.net.
Thanks a lot for your time and patience. Appreciate your help.

Answer 1

Borrowing from this question
Dim urlList As New List(Of String) 'Urls stored here
For each urlString as string in urlList
If CheckProxy(urlString) Then
'Execute the response
else
Continue For 'or something else here, mark it as bad?
End If
next
Public Shared Function CheckProxy(ByVal Proxy As String) As Boolean
Dim prx As Uri = Nothing
If Uri.TryCreate(Proxy, UriKind.Absolute, prx) Then
Return CheckProxy(prx)
ElseIf Uri.TryCreate("http://" & Proxy, UriKind.Absolute, prx) Then
Return CheckProxy(prx)
Else
Return False
End If
End Function
Public Shared Function CheckProxy(ByVal Proxy As Uri) As Boolean
Dim iProxy As Socket = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
iProxy.ReceiveTimeout = 500 : iProxy.SendTimeout = 500
Try
'' Connect using a timeout (1/2 second)
Dim result As IAsyncResult = iProxy.BeginConnect(Proxy.Host, Proxy.Port, Nothing, Nothing)
Dim success As Boolean = result.AsyncWaitHandle.WaitOne(500, True)
If (Not success) Then
iProxy.Close() : Return False
End If
Catch ex As Exception
Return False
End Try
Dim bytData() As Byte, strData As String
Dim iDataLen As Integer = 1024
strData = String.Format("CONNECT {0}:{1} HTTP/1.0{2}{2}", "www.google.com", 80, vbNewLine)
bytData = System.Text.ASCIIEncoding.ASCII.GetBytes(strData)
If iProxy.Connected Then
iProxy.Send(bytData, bytData.Length, SocketFlags.None)
ReDim bytData(1024)
Do
Try
iDataLen = iProxy.Receive(bytData, bytData.Length, SocketFlags.None)
Catch ex As Exception
iProxy.Close() : Return False
End Try
If iDataLen > 0 Then
strData = System.Text.ASCIIEncoding.ASCII.GetString(bytData)
Exit Do
End If
Loop
Else
Return False
End If
iProxy.Close()
Dim strAttribs() As String
strAttribs = strData.Split(" "c)
If strAttribs(1).Equals("200") Then
Return True
Else
Return False
End If
End Function