Socket.Bind for Multi NIC Setup For Connecting, not Listening.

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  14 years ago

  by Nick Kusters

  Nick Kusters

  Leiden, The Netherlands, Netherlands

  Joined 14 years ago

  I also posted this quesion in the Microsoft Newsgroup, but stuck out on an answer. [link]

   

  My problem is that i am unable to bind a socket to a Local IP Endpoint that is not 'my current link to the outside world'.

  Overview:

  3Com NIC, hooked up to my ADSL Router [ip: 192.168.1.33, External Ip: 83.160.*].
  LinkSys 802.11b/g wlan usb adapter, connected to a different ADSL Router [ip: 10.0.0.5, External IP: <can't remember, but also an online ip>]
  

  I made a small tool that would allow me to pick one of the IP's that are available on my system (as long as they are IPv4), bind to it (allowing the .NET framework to pick a port), connecting to a webserver, pulling some HTML data, and return a part of it to the Main Form.

  This works for my main NIC, but it will hang on Socket.Connect (right after bind), when i unplug my LAN, and the WLAN becomes the main source for internet access, it works for the WLAN card...

  The Main form only has a ComboBox named 'cboIPs', a Label named 'lblExternalIP' and two Buttons named 'btnRefresh' and 'btnGetExternal'.

  Here's the source i used:

  Class:

  Imports

  System.Diagnostics

  Imports

  System.net

  Imports

  System.net.sockets

  Namespace

  NKCSS.NET

  Public Class MultiIP

  Public Function AvailableIPs() As System.Net.IPAddress()

  Dim strMachineName As String

  'Get the Host Name

  strMachineName = Dns.GetHostName()

  Debug.WriteLine(

  "Host Name: " + strMachineName)

  'Get the Host by Name

  Dim ipHost As IPHostEntry

  ipHost = Dns.GetHostEntry(strMachineName)

  'Get the list of addresses associated with the host in an array

  Dim ipAddr() As System.Net.IPAddress = ipHost.AddressList

  Dim count As Integer

  'Enumerate the IP Addresses

  For count = 0 To ipAddr.Length - 1

  Debug.WriteLine(

  String.Format("IP Addresses {0}: {1} ", count, ipAddr(count).ToString))

  Next

  Return ipAddr

  End Function

  Public Function GetExternalIP(ByVal IP As IPAddress) As String

  If Not IP.AddressFamily = System.Net.Sockets.AddressFamily.InterNetwork Then Throw New Exception("IPv4 Only for now!")

  Dim Server As String = "www.whatismyip.com"

  Dim S As New System.Net.Sockets.Socket(IP.AddressFamily, SocketType.Stream, ProtocolType.Tcp)

  S.Bind(

  New System.Net.IPEndPoint(IP, 0))

  System.Diagnostics.Debug.WriteLine(S.LocalEndPoint)

  S.Connect(Server, 80)

  Dim Req As String = String.Format("GET / HTTP/1.1{0}Host: {1}{0}Connection: Close{0}{0}", vbCrLf, Server)

  Dim SendBuffer As [Byte]() = System.Text.Encoding.ASCII.GetBytes(Req)

  Dim ReceiveBuffer(255) As [Byte]

  S.Send(SendBuffer, SendBuffer.Length, 0)

  Dim BytesLeft As Int32

  Dim page As String = ""

  Do

  BytesLeft = S.Receive(ReceiveBuffer, ReceiveBuffer.Length, 0)

  page &= System.Text.Encoding.ASCII.GetString(ReceiveBuffer, 0, BytesLeft)

  Loop While BytesLeft > 0

  Dim Pattern As String = "<title>whatismyip\.com\s-\s(?<ip>.*?)</title>"

  Dim Regex As New System.Text.RegularExpressions.Regex(Pattern)

  Dim Match As System.Text.RegularExpressions.Match = Regex.Match(page.ToLower)

  If Match.Success Then

  Return Match.Groups("ip").Value

  Else

  Return "Unable to resolve"

  End If

  ' Return page

  End Function

  End Class

  End

  Namespace

   

  Main Form:

  Public

  Class Form1

  Dim i As New NKCSS.NET.MultiIP

  Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

  ' Refresh the available IP list.

  RefreshIPs()

  End Sub

  Private Sub btnRefresh_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnRefresh.Click

  ' Refresh the available IP list.

  RefreshIPs()

  End Sub

  Private Sub RefreshIPs()

  ' Remove the current selection

  cboIPs.SelectedIndex = -1

  ' Clear all present items

  cboIPs.Items.Clear()

  ' Walk thru all the ip's

  For Each IP As System.Net.IPAddress In i.AvailableIPs()

  ' Only add IPv4 addresses for now...

  If IP.AddressFamily = Net.Sockets.AddressFamily.InterNetwork Then

  cboIPs.Items.Add(IP)

  End If

  Next

  End Sub

  Private Sub btnGetExternal_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGetExternal.Click

  Dim eIP As String = i.GetExternalIP(CType(cboIPs.SelectedItem, System.Net.IPAddress))

  Debug.WriteLine(eIP)

  lblExternalIP.Text = eIP

  End Sub

  End

  Class

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