Using Windows Socket we can connect to any destination via Socks Proxy.
How it works:
Connecting without proxy:
1. Request Connection to DestinationServer:DestinationPort
2. Destination Connected
3. Start Receiving/Sending Data to Destination
Connecting with proxy:
1. Request Connection to ProxyServer:ProxyPort
2. If needed, provide Authentication Details for proxy server
3. ProxyServer connected
4. Passing our DestinationServer/port Details to Proxy Server
5. ProxyServer itself connects to the DestinationServer
6. Start Receiving/Sending Data to Destination
Code
Lets have 2 reusable class files for Proxy Connection
Proxy.vb
Public MustInherit Class Proxy
Private _server As String
Private _port As Integer
Private _user As String
Private _password As String
Public Property Server() As String
Get
Return _server
End Get
Set(ByVal value As String)
_server = value
End Set
End Property
Public Property Port() As Integer
Get
Return _port
End Get
Set(ByVal value As Integer)
_port = value
End Set
End Property
Public Property User() As String
Get
Return _user
End Get
Set(ByVal value As String)
_user = User
End Set
End Property
Public Property Password() As String
Get
Return _password
End Get
Set(ByVal value As String)
_password = Password
End Set
End Property
Public ReadOnly Property ProxyIPEndPoint() As IPEndPoint
Get
Return New IPEndPoint(Dns.GetHostEntry(_server).AddressList(0), _port)
End Get
End Property
Public Sub New(ByVal Server As String, ByVal Port As Integer, ByVal User As String, ByVal Password As String)
_server = Server
_port = Port
_user = User
_password = Password
End Sub
End Class
SocksProxy.vb
Imports System.Net.Sockets
Imports System.Net
Imports System.Text
Public Class SocksProxy
Inherits Proxy
Private _cSocket As Socket
Private _destHost As String
Private _destPort As String
Enum ProxyState
RequestAuthenticate
Authenticate
ConnectServer
Done
End Enum
Private sPxy As ProxyState
Private Const BUFFER_SIZE As Integer = 512
Private transferBuffer(BUFFER_SIZE) As Byte
Public Event Completed(ByVal sender As Object, ByVal e As SocketAsyncEventArgs)
Public Sub New(ByVal Server As String, ByVal Port As Integer, ByVal User As String, ByVal Password As String)
MyBase.New(Server, Port, User, Password)
End Sub
Public Sub New(ByVal p As Proxy)
MyBase.New(p.Server, p.Port, p.User, p.Password)
End Sub
Public Sub Connect(ByVal s As Socket, ByVal destHost As String, ByVal destPort As Integer)
Dim connectEventArgs As New SocketAsyncEventArgs
_destHost = destHost
_destPort = destPort
_cSocket = s
connectEventArgs.RemoteEndPoint = ProxyIPEndPoint
AddHandler connectEventArgs.Completed, AddressOf connectEventProxyArgs_Completed
_cSocket.ConnectAsync(connectEventArgs)
End Sub
#Region "SOCKS5 Proxy Functions"
Private Sub connectEventProxyArgs_Completed(ByVal sender As Object, ByVal e As SocketAsyncEventArgs)
If e.SocketError <> SocketError.Success Then
Throw New Exception(e.SocketError.ToString)
Return
End If
RemoveHandler e.Completed, AddressOf connectEventProxyArgs_Completed
AddHandler e.Completed, AddressOf receiveEventProxyArgs_Completed
e.SetBuffer(transferBuffer, 0, transferBuffer.Length)
_cSocket.ReceiveAsync(e)
sPxy = ProxyState.RequestAuthenticate
sendProxyData()
End Sub
Private Sub receiveEventProxyArgs_Completed(ByVal sender As Object, ByVal e As SocketAsyncEventArgs)
If e.SocketError <> SocketError.Success Then
Throw New Exception(e.SocketError.ToString)
Return
End If
Try
Dim bRec(e.BytesTransferred) As Byte
Buffer.BlockCopy(transferBuffer, e.Offset, bRec, 0, e.BytesTransferred)
Process_Proxy_Data(bRec, e)
If sPxy <> ProxyState.Done Then _cSocket.ReceiveAsync(e)
Catch ex As Exception
Throw New Exception(ex.Message)
End Try
End Sub
Private Sub sendProxyData()
Dim request(257) As Byte
Dim rawBytes() As Byte
Dim nIndex As UShort = 0
Try
Select Case sPxy
Case ProxyState.RequestAuthenticate
request(nIndex) = &H5 : nIndex += 1 ' Version 5.
If User <> "" Then 'only if provided
request(nIndex) = &H2 : nIndex += 1 ' 2 Authentication methods are in packet...
request(nIndex) = &H0 : nIndex += 1 ' NO AUTHENTICATION REQUIRED
request(nIndex) = &H2 : nIndex += 1 ' USERNAME/PASSWORD
Else
request(nIndex) = &H1 : nIndex += 1 ' 1 Authentication method in packet...
request(nIndex) = &H0 : nIndex += 1 ' NO AUTHENTICATION REQUIRED
End If
' Send the authentication negotiation request...
_cSocket.Send(request, nIndex, SocketFlags.None)
Case ProxyState.Authenticate
'Username/Password Authentication protocol
request(nIndex) = &H1 : nIndex += 1 ' Current version of the subnegotiation.
' add user name
request(nIndex) = CType(User.Length, Byte) : nIndex += 1
rawBytes = Encoding.Default.GetBytes(User)
rawBytes.CopyTo(request, nIndex)
nIndex += CType(rawBytes.Length, UShort)
' add password
request(nIndex) = CType(Password.Length, Byte) : nIndex += 1
rawBytes = Encoding.Default.GetBytes(Password)
rawBytes.CopyTo(request, nIndex)
nIndex += CType(rawBytes.Length, UShort)
' Send the Username/Password request
_cSocket.Send(request, nIndex, SocketFlags.None)
Case ProxyState.ConnectServer
Dim destIP As IPAddress = Nothing
Try
destIP = IPAddress.Parse(_destHost)
Catch ex As Exception
End Try
request(nIndex) = &H5 : nIndex += 1 ' version 5.
request(nIndex) = &H1 : nIndex += 1 ' command = connect.(connect=1; bind=2; UDP=3)
request(nIndex) = &H0 : nIndex += 1 ' Reserve = must be 0x00
If (Not destIP Is Nothing) Then
' Destination adress in an IP.
Select Case (destIP.AddressFamily)
Case AddressFamily.InterNetwork
' Address is IPV4 format(IP-V4=1; domain name=3; IP-V6=4)
request(nIndex) = &H1 : nIndex += 1
rawBytes = destIP.GetAddressBytes()
rawBytes.CopyTo(request, nIndex)
nIndex += CType(rawBytes.Length, UShort)
Case AddressFamily.InterNetworkV6
' Address is IPV6 format
request(nIndex) = &H4 : nIndex += 1
rawBytes = destIP.GetAddressBytes()
rawBytes.CopyTo(request, nIndex)
nIndex += CType(rawBytes.Length, UShort)
End Select
Else
' Dest. address is domain name.
request(nIndex) = &H3 : nIndex += 1 ' Address is full-qualified domain name.
request(nIndex) = Convert.ToByte(_destHost.Length) : nIndex += 1 ' length of addres_cSocket.
rawBytes = Encoding.Default.GetBytes(_destHost)
rawBytes.CopyTo(request, nIndex)
nIndex += CType(rawBytes.Length, Short)
End If
request(nIndex) = Convert.ToByte((_destPort And &HFF00) >> 8) : nIndex += 1
request(nIndex) = Convert.ToByte(_destPort And &HFF) : nIndex += 1
' send connect request.
_cSocket.Send(request, nIndex, SocketFlags.None)
End Select
Catch ex As Exception
Throw New Exception(ex.Message)
End Try
End Sub
Private Sub Process_Proxy_Data(ByVal pMessage() As Byte, ByVal e As SocketAsyncEventArgs)
If pMessage.Length < 2 Then Return
Dim response(257) As Byte
Dim nIndex As UShort = 0
Select Case sPxy
Case ProxyState.RequestAuthenticate
If pMessage(1) = &H0 Then
'No Authentication required
sPxy = ProxyState.ConnectServer
sendProxyData()
ElseIf pMessage(1) = &H2 Then
'Authentication required
sPxy = ProxyState.Authenticate
sendProxyData()
Else
Throw New Exception("None of the authentication method was accepted by proxy server.")
End If
Case ProxyState.Authenticate
If pMessage(1) = &H0 Then
'Authentication Success
sPxy = ProxyState.ConnectServer
sendProxyData()
Else
Throw New Exception("Bad Username/Password.")
End If
Case ProxyState.ConnectServer
If pMessage(1) = &H0 Then
'Connected
' Change the Handler to Regular Receive Event
RemoveHandler e.Completed, AddressOf receiveEventProxyArgs_Completed
sPxy = ProxyState.Done
RaiseEvent Completed(_cSocket, e)
Else
Throw New Exception("Unable to connect Proxy Server.")
End If
End Select
End Sub
#End Region
End Class
After including the above 2 class files, you can connect to a destination either directly or via proxy(if defined)
Public Class MyClass
Private _cSocket As Socket
Public Function Connect() As Boolean
Dim server As String = "[destinationServer]"
Dim port As Integer ="[destinationPort]"
Dim clientproxy As Proxy = Nothing
clientproxy=new Proxy("[proxyServer]","[proxyPort]","[uname]","[pwd]")
_cSocket = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
Dim connectEventArgs As New SocketAsyncEventArgs
If clientproxy Is Nothing Then
connectEventArgs.RemoteEndPoint = New IPEndPoint(Dns.GetHostEntry(server).AddressList(0), port)
AddHandler connectEventArgs.Completed, AddressOf connectEventArgs_Completed
_cSocket.ConnectAsync(connectEventArgs)
Else
socksProxy = New SocksProxy(clientproxy)
AddHandler socksProxy.Completed, AddressOf connectEventArgs_Completed
socksProxy.Connect(_cSocket, server, port)
End If
Return True
End Function
Private Sub connectEventArgs_Completed(ByVal sender As Object, ByVal e As SocketAsyncEventArgs)
If e.SocketError = SocketError.Success Then
RemoveHandler e.Completed, AddressOf connectEventArgs_Completed
ReceiveBegin()
End If
End Sub
Private Sub ReceiveBegin()
..........
..........
Hope it is simple. Happy Programming!
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