Free Visual Basic ebook download

E-book. Free VB eBook - The most elementary single-thread Proxy in Visual Basic. In creating this manual we set ourselves the task to develop a minimum program code playing the role of Proxy-server (transmitting information from one port to another). It is easy to add filtration functions to the program (it will be shown in the supplement), log records, information substitution records (link addresses, advertisement in HTML - for web site promotion).

Free VB ebook Create standard Visual Basic project. Deploy element Label “this computer’s IP” on the form

Form

Connect a new Winsock component to the project for work with the network according to TCP/IP protocol

Project Components Winsock Control Component

Winsock - Winsock component

Free Visual Basic e-books

Deploy two Winsock copies on the form. Winsock1 – for the server part and Oflameron for the client part. The server part (Winsock1) receives queries from the Web-browser (for example, Internet Explorer) through the port, for example, 125 and transmits it to the client part. The client part Oflameron (Winsock2) through standard port 80 transmits queries to the real Web-server.




Ebooks Ebook >>
Ebooks VB e-book >>
Ebooks Free e-book >>
Ebooks E-books >>



Winsock

Write the Proxy server part

Private Sub Form_Load()
Form1.Visible = True
Do ''Switch the server part to port listening ( Listen )
If Winsock1.State <> sckConnected And Winsock1.State <> sckListening Then ''If there is no connection yet and the port cannot be heard
Beep
Winsock1.Close ''Close the connection
Winsock1.LocalPort = 125 ''Port number for listening
Winsock1.Listen ''Begin listening port 125
End If
DoEvents
Loop ''Repeat
End Sub

Connections processing

Private Sub Winsock1_ConnectionRequest(ByVal requestID As Long) ''If there is query for connection
Winsock1.Close ''Stop listening the port
Winsock1.Accept requestID ''Connect the client (browser) according to the number of the query
End Sub

Winsock1_ConnectionRequest – query for connection

Connection Request


Announce the variable
Dim ToServer As String ''To send the query from the client part of Proxy to Web-server


Private Sub Winsock1_DataArrival(ByVal bytesTotal As Long) ''Processing of incoming data (queries from Web-browser)
Dim ServerData As String ''Announce the variable for the received data ServerData
Winsock1.GetData ServerData ''Accept data into the variable
ToServer = ServerData ''Copy the query into the variable for sending to the Web-server
Oflameron_SendToWebserver ''Send the query to the Web-server
End Sub

Line “ToServer = ServerData” - is not mandatory, it is worthwhile, if it is necessary to process data writing in the log, filter, search for data in queries, substitute information (for example, change URL in downloaded web-pages for one’s own) etc.

The entire VB project of this development stage is in the file vbpt1.zip

Free VB ebooks


Write the Client part of Proxy

For work with real Web-server. Connection to Web-server, sending of queries and data receipt.

Announce the variables

Dim Webport ''Port number
Dim Data As String ''To receive data from Web-server

Private Sub Oflameron_SendToWebserver() ''Connect to Web-server
Oflameron.Close ''Close the connection
Oflameron.RemoteHost = "10.62.182.54" ''Web-server address or its IP address
Oflameron.RemotePort = 80 ''Port number. Standard for HTTP
Oflameron.Connect ''Connect to Web-server
Webport = Oflameron.RemotePort ''Remember the port number (optional line)
End Sub

Procedure Oflameron_Connect performs actions as soon as the Web-server is connected

Private Sub Oflameron_Connect() ''Sent query to Web-server
If Oflameron.State <> sckConnected Then Exit Sub ''Check. If there is no connection, abandon the procedure
Oflameron.SendData ToServer ''Send the query line to the Web-server
End Sub

The procedure of data receipt from the Web-server

Private Sub Oflameron_DataArrival(ByVal bytesTotal As Long) ''The call will be initiated as soon as some data is received from the Web-server
Text1.Text = Oflameron.State
If Oflameron.State <> sckClosing Then
Oflameron.GetData Data ''It will contain data obtained from the Web-server
Winsock1.SendData Data ''Send the obtained data from Web server to Web-browser
End If
End Sub


HTTP- put port number 125 for the server part of Proxy

Change Proxy and port settings in Internet Explorer, if you use IE

Browser

So that queries were sent to our Proxy

LAN

LAN adjustment

IP

Where LAN - the address of our Proxy (IP-address of your computer) and port 125, which will listen to the server part of your Proxy

Upload the page from the Web-server to Internet Explorer website

Website

Proxy-server operates –sends queries and received data.

Visual Basic ebooks

This is a working example of a most elementary Proxy-server in the minimal code configuration. It allows to understand important specifics of network programming, create a working copy of the program.