I am developing a program that gets the html source code of a certain webpages in a website.

I already developed one program that does so,
here's the sample code

     Dim request As System.Net.HttpWebRequest =     System.Net.HttpWebRequest.Create(TextBox2.Text)
     Dim response As System.Net.HttpWebResponse = request.GetResponse()

     Dim sr As System.IO.StreamReader = New      System.IO.StreamReader(response.GetResponseStream())

     Dim sourcecode As String = sr.ReadToEnd()
     TextBox1.Text = sourcecode

Recently, I found out that I could do the same using Sockets. This time I want to parse HTML of those web pages SIMULTANEOUSLY. I tried parsing simultaneously on my previous program using multithreading but my bandwidth keeps decreasing as threads increase so, to make my questions short,

*** How can I parse many web pages' source SIMULTANEOUSLY without decreasing my Bandwidth?
* Does using Sockets in multi threading decrease Bandwidth? (If anyone tried)**

If my question wasn't clear, please feel free to correct me and I'd gladly accept any advice you can give.