Introduction:
This tutorial will be on how to create a proxy checker which will test a list of proxies and report if they respond within 3000ms/3seconds (can be changed using .Timeout).

Steps of Creation:
Step 1:
First we will need to Import two packages, one to use StreamReader and StreamWriter and another to use HttpWebRequest and HttpWebResponse

1. Imports System.IO
   
2. Imports System.Net
   

Step 2:
Add a listbox and three buttons. The listbox will contains the reports of each proxy and the button will be for; Starting the checker, Exporting all the reports and Exporting the working reports
First lets make the start script. Let's create an openFileDialog to select a proxy list and check the path isn't nothing/null/empty:

1. Private
   
   Sub
   
   Button1_Click(sender As
   
   Object
   
   , e As
   
   EventArgs) Handles Button1.Click
   
2. Dim
   
   fo As
   
   New
   
   OpenFileDialog
   
3. fo.RestoreDirectory = True
   
4. fo.Multiselect = False
   
5. fo.Filter = "txt files (*.txt)|*.txt"
   
6. fo.FilterIndex = 1
   
7. fo.ShowDialog()
   
8. If
   
   (Not
   
   fo.FileName = Nothing
   
   ) Then
   
9. End
   
   If
   
10. End
    
    Sub
    

Step 3:
Now let's create a new "proxies" String List and add all the lines of the file in to the list.

1. Private
   
   Sub
   
   Button1_Click(sender As
   
   Object
   
   , e As
   
   EventArgs) Handles Button1.Click
   
2. Dim
   
   fo As
   
   New
   
   OpenFileDialog
   
3. fo.RestoreDirectory = True
   
4. fo.Multiselect = False
   
5. fo.Filter = "txt files (*.txt)|*.txt"
   
6. fo.FilterIndex = 1
   
7. fo.ShowDialog()
   
8. If
   
   (Not
   
   fo.FileName = Nothing
   
   ) Then
   
9. Dim
   
   proxies As
   
   New
   
   List(Of String
   
   )
   
10. Using sr As
    
    New
    
    StreamReader(fo.FileName)
    
11. While
    
    sr.Peek <> -1
    
12. proxies.Add(sr.ReadLine())
    
13. End
    
    While
    
14. End
    
    Using
    
15. End
    
    If
    
16. End
    
    Sub
    

Step 3:
For the last bit of the checking script let's create a HTTPWebRequest to Google, set the proxy to the current address and set a timeout for the request of receiving the response to 3000ms/3seconds. If it gets a response it will continue and add the proxy as "Working" to the list box, otherwise it will catch the error and report it as "Unresponsive".

1. Private
   
   Sub
   
   Button1_Click(sender As
   
   Object
   
   , e As
   
   EventArgs) Handles Button1.Click
   
2. Dim
   
   fo As
   
   New
   
   OpenFileDialog
   
3. fo.RestoreDirectory = True
   
4. fo.Multiselect = False
   
5. fo.Filter = "txt files (*.txt)|*.txt"
   
6. fo.FilterIndex = 1
   
7. fo.ShowDialog()
   
8. If
   
   (Not
   
   fo.FileName = Nothing
   
   ) Then
   
9. Dim
   
   proxies As
   
   New
   
   List(Of String
   
   )
   
10. Using sr As
    
    New
    
    StreamReader(fo.FileName)
    
11. While
    
    sr.Peek <> -1
    
12. proxies.Add(sr.ReadLine())
    
13. End
    
    While
    
14. End
    
    Using
    
15. Dim
    
    myProxy As
    
    WebProxy
    
16. For
    
    Each
    
    proxy As
    
    String
    
    In
    
    proxies
    
17. Try
    
18. myProxy = New
    
    WebProxy(proxy)
    
19. Dim
    
    r As
    
    HttpWebRequest = HttpWebRequest.Create("http://www.google.com"
    
    )
    
20. r.UserAgent = "Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/29.0.1547.2 Safari/537.36"
    
21. r.Timeout = 3000
    
22. r.Proxy = myProxy
    
23. Dim
    
    re As
    
    HttpWebResponse = r.GetResponse()
    
24. ListBox1.Items.Add("Working Proxy: "
    
    & proxy)
    
25. Catch ex As
    
    Exception
    
26. ListBox1.Items.Add("Unresponsive Proxy: "
    
    & proxy)
    
27. End
    
    Try
    
28. Next
    
29. End
    
    If
    
30. End
    
    Sub
    

Step 4:
Now let's make a quick export all script. A simple script to select a save file, iterate through all the items in the listbox and write the line to the file using StreamWriter:

1. Private
   
   Sub
   
   Button2_Click(sender As
   
   Object
   
   , e As
   
   EventArgs) Handles Button2.Click
   
2. If
   
   (ListBox1.Items.Count > 0) Then
   
3. Dim
   
   fs As
   
   New
   
   SaveFileDialog
   
4. fs.RestoreDirectory = True
   
5. fs.Filter = "txt files (*.txt)|*.txt"
   
6. fs.FilterIndex = 1
   
7. fs.ShowDialog()
   
8. If
   
   Not
   
   (fs.FileName = Nothing
   
   ) Then
   
9. Using sw As
   
   New
   
   StreamWriter(fs.FileName)
   
10. For
    
    Each
    
    line
    
    As
    
    String
    
    In
    
    ListBox1.Items
    
11. sw.WriteLine(line
    
    )
    
12. Next
    
13. End
    
    Using
    
14. End
    
    If
    
15. End
    
    If
    
16. End
    
    Sub
    

Step 5:
Now for the export working proxies script. It's the exact same as the export all script except we want to check if the line starts with "Working Proxy: ". Alternatively we could setup a list and when we check them we could add the working ones to a list and read that.

1. Private
   
   Sub
   
   Button3_Click(sender As
   
   Object
   
   , e As
   
   EventArgs) Handles Button3.Click
   
2. If
   
   (ListBox1.Items.Count > 0) Then
   
3. Dim
   
   fs As
   
   New
   
   SaveFileDialog
   
4. fs.RestoreDirectory = True
   
5. fs.Filter = "txt files (*.txt)|*.txt"
   
6. fs.FilterIndex = 1
   
7. fs.ShowDialog()
   
8. If
   
   Not
   
   (fs.FileName = Nothing
   
   ) Then
   
9. Using sw As
   
   New
   
   StreamWriter(fs.FileName)
   
10. For
    
    Each
    
    line
    
    As
    
    String
    
    In
    
    ListBox1.Items
    
11. If
    
    (line
    
    .StartsWith("Working Proxy: "
    
    )) Then
    
    sw.WriteLine(line
    
    )
    
12. Next
    
13. End
    
    Using
    
14. End
    
    If
    
15. End
    
    If
    
16. End
    
    Sub
    

Project Completed!
That's it! Below is the source code and you can download the project from the attached files below.

1. Imports System.IO
   
2. Imports System.Net
   
3. Public
   
   Class Form1
   
4. Private
   
   Sub
   
   Button1_Click(sender As
   
   Object
   
   , e As
   
   EventArgs) Handles Button1.Click
   
5. Dim
   
   fo As
   
   New
   
   OpenFileDialog
   
6. fo.RestoreDirectory = True
   
7. fo.Multiselect = False
   
8. fo.Filter = "txt files (*.txt)|*.txt"
   
9. fo.FilterIndex = 1
   
10. fo.ShowDialog()
    
11. If
    
    (Not
    
    fo.FileName = Nothing
    
    ) Then
    
12. Dim
    
    proxies As
    
    New
    
    List(Of String
    
    )
    
13. Using sr As
    
    New
    
    StreamReader(fo.FileName)
    
14. While
    
    sr.Peek <> -1
    
15. proxies.Add(sr.ReadLine())
    
16. End
    
    While
    
17. End
    
    Using
    
18. Dim
    
    myProxy As
    
    WebProxy
    
19. For
    
    Each
    
    proxy As
    
    String
    
    In
    
    proxies
    
20. Try
    
21. myProxy = New
    
    WebProxy(proxy)
    
22. Dim
    
    r As
    
    HttpWebRequest = HttpWebRequest.Create("http://www.google.com"
    
    )
    
23. r.UserAgent = "Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/29.0.1547.2 Safari/537.36"
    
24. r.Timeout = 3000
    
25. r.Proxy = myProxy
    
26. Dim
    
    re As
    
    HttpWebResponse = r.GetResponse()
    
27. ListBox1.Items.Add("Working Proxy: "
    
    & proxy)
    
28. Catch ex As
    
    Exception
    
29. ListBox1.Items.Add("Unresponsive Proxy: "
    
    & proxy)
    
30. End
    
    Try
    
31. Next
    
32. End
    
    If
    
33. End
    
    Sub
    
34. 
    
35. Private
    
    Sub
    
    Button2_Click(sender As
    
    Object
    
    , e As
    
    EventArgs) Handles Button2.Click
    
36. If
    
    (ListBox1.Items.Count > 0) Then
    
37. Dim
    
    fs As
    
    New
    
    SaveFileDialog
    
38. fs.RestoreDirectory = True
    
39. fs.Filter = "txt files (*.txt)|*.txt"
    
40. fs.FilterIndex = 1
    
41. fs.ShowDialog()
    
42. If
    
    Not
    
    (fs.FileName = Nothing
    
    ) Then
    
43. Using sw As
    
    New
    
    StreamWriter(fs.FileName)
    
44. For
    
    Each
    
    line
    
    As
    
    String
    
    In
    
    ListBox1.Items
    
45. sw.WriteLine(line
    
    )
    
46. Next
    
47. End
    
    Using
    
48. End
    
    If
    
49. End
    
    If
    
50. End
    
    Sub
    
51. 
    
52. Private
    
    Sub
    
    Button3_Click(sender As
    
    Object
    
    , e As
    
    EventArgs) Handles Button3.Click
    
53. If
    
    (ListBox1.Items.Count > 0) Then
    
54. Dim
    
    fs As
    
    New
    
    SaveFileDialog
    
55. fs.RestoreDirectory = True
    
56. fs.Filter = "txt files (*.txt)|*.txt"
    
57. fs.FilterIndex = 1
    
58. fs.ShowDialog()
    
59. If
    
    Not
    
    (fs.FileName = Nothing
    
    ) Then
    
60. Using sw As
    
    New
    
    StreamWriter(fs.FileName)
    
61. For
    
    Each
    
    line
    
    As
    
    String
    
    In
    
    ListBox1.Items
    
62. If
    
    (line
    
    .StartsWith("Working Proxy: "
    
    )) Then
    
    sw.WriteLine(line
    
    )
    
63. Next
    
64. End
    
    Using
    
65. End
    
    If
    
66. End
    
    If
    
67. End
    
    Sub
    
68. End
    
    Class
    

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