Newbie lost in socket programming with error "An existing connection was forcibly closed by the remote host"

Newbie lost in socket programming with error "An existing connection was forcibly closed by the remote host"

• Birkbaum

  I've been trying this code today... Unsuccessful as well

  Dim ServerSocket As System.Net.Sockets.Socket = New System.Net.Sockets.Socket(Net.Sockets.AddressFamily.InterNetwork, Net.Sockets.SocketType.Stream, Net.Sockets.ProtocolType.Tcp)

  Dim ClientSocket As System.Net.Sockets.Socket = New System.Net.Sockets.Socket(Net.Sockets.AddressFamily.InterNetwork, Net.Sockets.SocketType.Stream, Net.Sockets.ProtocolType.Tcp)

  Dim LocalIPEndPoint As System.Net.IPEndPoint = New System.Net.IPEndPoint(System.Net.IPAddress.Loopback, 81)

  Dim S_Bytes(4096) As [Byte]

  Dim C_Bytes(4096) As [Byte]

  Dim AcceptSocket As System.Net.Sockets.Socket

  Dim S_NetStream As System.Net.Sockets.NetworkStream, C_NetStream As System.Net.Sockets.NetworkStream

  ServerSocket.Blocking = True

  ClientSocket.Blocking = True

  ServerSocket.Bind(LocalIPEndPoint)

  ServerSocket.Listen(10)

  Do

  AcceptSocket = ServerSocket.Accept()

  S_NetStream = New System.Net.Sockets.NetworkStream(AcceptSocket, True)

  S_NetStream.ReadTimeout = 5000

  S_NetStream.WriteTimeout = 5000

  ClientSocket.Connect("192.168.1.1", 80)

  C_NetStream = New System.Net.Sockets.NetworkStream(ClientSocket)

  C_NetStream.ReadTimeout = 5000

  C_NetStream.WriteTimeout = 5000

  If (ClientSocket.Connected = True) Then

  While ((AcceptSocket.Connected = True) And (ClientSocket.Connected = True))

  While (S_NetStream.DataAvailable = True)

  S_NetStream.Read(S_Bytes, 0, S_Bytes.Length)

  C_NetStream.Write(S_Bytes, 0, S_Bytes.Length)

  If (C_NetStream.DataAvailable = True) Then

  C_NetStream.Read(C_Bytes, 0, C_Bytes.Length)

  S_NetStream.Write(C_Bytes, 0, C_Bytes.Length)

  End If

  End While

  System.Threading.Thread.Sleep(50)

  End While

  End If

  C_NetStream.Close()

  C_NetStream.Dispose()

  S_NetStream.Close()

  S_NetStream.Dispose()

  ClientSocket.Close()

  Loop

  
  

• Derek Chan

  Hi,

  Indeed, I forgot to highlight where the error occurs... Sorry

  Actually, there is definitelly no error message... For what matters the [Byte], I copied it from Microsoft Sample code; it looks to be the same as you defined above (as Byte {})

  Cheers

  Dim ServerSocket As System.Net.Sockets.Socket = New System.Net.Sockets.Socket(Net.Sockets.AddressFamily.InterNetwork, Net.Sockets.SocketType.Stream, Net.Sockets.ProtocolType.Tcp)

  Dim ClientSocket As System.Net.Sockets.Socket = New System.Net.Sockets.Socket(Net.Sockets.AddressFamily.InterNetwork, Net.Sockets.SocketType.Stream, Net.Sockets.ProtocolType.Tcp)

  Dim LocalIPEndPoint As System.Net.IPEndPoint = New System.Net.IPEndPoint(System.Net.IPAddress.Loopback, 81)

  Dim S_Bytes(4096) As [Byte]

  Dim C_Bytes(4096) As [Byte]

  Dim AcceptSocket As System.Net.Sockets.Socket

  Dim S_NetStream As System.Net.Sockets.NetworkStream, C_NetStream As System.Net.Sockets.NetworkStream

  ServerSocket.Blocking = True

  ClientSocket.Blocking = True

  ServerSocket.Bind(LocalIPEndPoint)

  ServerSocket.Listen(10)

  Do

  AcceptSocket = ServerSocket.Accept()

  S_NetStream = New System.Net.Sockets.NetworkStream(AcceptSocket, True)

  S_NetStream.ReadTimeout = 5000

  S_NetStream.WriteTimeout = 5000

  ClientSocket.Connect("192.168.1.1", 80)

  C_NetStream = New System.Net.Sockets.NetworkStream(ClientSocket)

  C_NetStream.ReadTimeout = 5000

  C_NetStream.WriteTimeout = 5000

  If (ClientSocket.Connected = True) Then

  While ((AcceptSocket.Connected = True) And (ClientSocket.Connected = True))

  While (S_NetStream.DataAvailable = True)

  S_NetStream.Read(S_Bytes, 0, S_Bytes.Length) => On first, everything is perfect and the browser is well receiving data but on second loop the Listener freezes

  C_NetStream.Write(S_Bytes, 0, S_Bytes.Length)

  If (C_NetStream.DataAvailable = True) Then

  C_NetStream.Read(C_Bytes, 0, C_Bytes.Length)

  S_NetStream.Write(C_Bytes, 0, C_Bytes.Length)

  End If

  End While

  System.Threading.Thread.Sleep(50)

  End While

  End If

  C_NetStream.Close()

  C_NetStream.Dispose()

  S_NetStream.Close()

  S_NetStream.Dispose()

  ClientSocket.Close()

  Loop

  
  

• SeveQ

  hi ,
  loooool i asked you wich line your program doesn't response and you never mentioned this, but you said in first loop its ok but in second loop your program die
  
  
  

• advind

  Hi,

  I've got the impression I'm getting silly

  The code below is running (most of the time) BUT depending on the sleep time ( ). If no sleep time, the browser doesn't receive anything, sleep time to 250 milliseconds and it is OK...

  Private Const SleepTime As Long = 0

  Private Const RemoteHost As String = "192.168.1.110"

  Private Const RemotePort As Integer = 80

  Dim ServerSocket As System.Net.Sockets.Socket

  Dim LocalIPEndPoint As System.Net.IPEndPoint

  Dim ClientSocket As System.Net.Sockets.Socket

  Dim Bytes() As Byte

  Dim AcceptSocket As System.Net.Sockets.Socket

  Dim Decoded As String

  ServerSocket = New System.Net.Sockets.Socket(Net.Sockets.AddressFamily.InterNetwork, Net.Sockets.SocketType.Stream, Net.Sockets.ProtocolType.Tcp)

  LocalIPEndPoint = New System.Net.IPEndPoint(System.Net.IPAddress.Any, 81)

  ServerSocket.Bind(LocalIPEndPoint)

  ServerSocket.Listen(1000)

  Me.Text = "Listening on " & ServerSocket.LocalEndPoint.ToString & "..."

  Me.Refresh()

  Do

  Dim TransBytes As Integer = 0

  ClientSocket = New System.Net.Sockets.Socket(Net.Sockets.AddressFamily.InterNetwork, Net.Sockets.SocketType.Stream, Net.Sockets.ProtocolType.Tcp)

  AcceptSocket = ServerSocket.Accept()

  'AcceptSocket.Blocking = False

  ClientSocket.Connect(RemoteHost, RemotePort)

  If (Not ClientSocket.Connected) Then

  MsgBox("Client socket failure !", MsgBoxStyle.Critical)

  End If

  If (ClientSocket.Connected = True) Then

  'ClientSocket.Blocking = False

  While ((AcceptSocket.Connected = True) And (ClientSocket.Connected = True))

  If ((AcceptSocket.Available = 0) And (ClientSocket.Available = 0)) Then

  Exit While

  End If

  While (AcceptSocket.Available > 0)

  Bytes = New Byte(AcceptSocket.Available) {}

  TransBytes = AcceptSocket.Receive(Bytes)

  ClientSocket.Send(Bytes)

  Decoded = System.Text.Encoding.Default.GetString(Bytes)

  Debug.Print("----------S Packet_0:" & vbCrLf & Decoded & vbCrLf & "----------" & vbCrLf)

  System.Threading.Thread.Sleep(SleepTime)

  Erase Bytes

  End While

  System.Threading.Thread.Sleep(SleepTime)

  While (ClientSocket.Available > 0)

  Bytes = New Byte(ClientSocket.Available) {}

  TransBytes = ClientSocket.Receive(Bytes)

  AcceptSocket.Send(Bytes)

  Decoded = System.Text.Encoding.Default.GetString(Bytes)

  Debug.Print("----------C Packet_0:" & vbCrLf & Decoded & vbCrLf & "----------" & vbCrLf)

  System.Threading.Thread.Sleep(SleepTime)

  Erase Bytes

  End While

  End While

  End If

  ClientSocket.Shutdown(Net.Sockets.SocketShutdown.Both)

  ClientSocket.Disconnect(True)

  AcceptSocket.Shutdown(Net.Sockets.SocketShutdown.Both)

  AcceptSocket.Disconnect(True)

  Loop

  
  

• Adam Mishler

  hi,

  i guess this is the reason

  you wrote something strange to me Dim SBuffer(4096) As [Byte], CBuffer(4096) As [Byte]

  what is this [byte] anyway you have to declare it and in each loop you have to reconstract the byte array or it will give you a headache

  Dim SBuffer As Byte()

  While (aSocket.Connected = True)

  Do

  SBuffer = New Byte(1024) {}

  SBytes = aSocket.Receive(sBuffer, 0, sBuffer.Length, Net.Sockets.SocketFlags.None)

  
hope this helps

  
  
  

• CSharpner

  hi,

  sure because sockets are blocking by default i don't think you should declare that either because its default value

  more over the sockets.read returns values represent the number of bytes recieved you can use this

  here its an echo server program that i has it accept a text message then send it back to the client as its (you can change this part to send it to particular server) then it convert the bytes to string for console to writeLine("you don't need this part")

  Namespace NetWorkingServers     Imports System.Net Imports System.Text     Imports System.Net.Sockets     Imports System.Threading               Class E1_ThreadedTCPServer                  Private srvr As TcpListener                  Public Sub New()             MyBase.New             srvr = New TcpListener(1234)             srvr.Start             Console.WriteLine("Waiting for Clients ...")                          While true                 'keep looping till the server recieve request for connection                                  While Not srvr.Pending                     Thread.Sleep(1000)                                      End While                 'creat instance of the other class                 Dim newconnection As connectionThread = New connectionThread                 newconnection.threadListener = Me.srvr                 Dim newthread As Thread = New Thread(New ThreadStart(newconnection.HandleConnection))                 newthread.Start                              End While         End Sub     End Class          'E1_threadedServer     Class connectionThread                  Public threadListener As TcpListener                  Private Shared connections As Integer = 0                  Public Sub HandleConnection()             Dim recv As Integer             Dim data() As Byte = New Byte(1024) {}             Dim client As TcpClient = threadListener.AcceptTcpClient             Dim ns As NetworkStream = client.GetStream             connections +=  1             Console.WriteLine("New client Accepted: {0} Active connections", connections)             'send welcome message             Dim strdata As String = "Welcome to my Threaded Server"             data = Encoding.UTF8.GetBytes(strdata)             ns.Write(data, 0, data.Length)             ' send and recieve                          While true                 data = New Byte(1024) {}                 recv = ns.Read(data, 0, data.Length)                  'if client is no more active kill this connection                 If (recv = 0) Then                     Exit while                 End If                 strdata = Encoding.UTF8.GetString(data, 0, recv)                 Console.WriteLine(strdata)                 ns.Write(data, 0, recv)                              End While             'close every thing             connections = (connections - 1)             Console.WriteLine("Client Disconnected : {0} Active Connections", connections)             ns.Close             client.Close             'ToDo : Aport thread         End Sub     End Class End Namespace

  hope this helps

  
  
  

• JPulham

  hi,

  i use this part to check if the client closed hte connection

  While true                  'if client is no more active kill this connection                 If (recv = 0) Then                     Exit while                 End If                  'ToDO : recieve of send data                          End While

  i think when tcp close connection is it send a close packet which dosn't contain any data so if the data in the packet = 0 then its closing connection packet

  i use this and it works,

  one more thing your code will give you a headache if it worked you will find the messages will appear in the textbox in funny way

  no way to gurantee the message will be recieved as you send it with tcp, and the array will initiate all elments so if you program recieved hello it will read it ("hello  'space' * 4029" ) the space will be repeated as much as the array elements    so you have to manuplate it during encoding like this System.Text.Encoding.Default.GetString(Data,0, recv) or you will get all those white spaces

  you can use string.trim but this is wast of time why you have to read it and then trim it , just read the avilable data 

  hope this helps

  
  
  

• erivas

  hi,

  first of all when you use TCP\IP there is no gurantee that the data will be delivered as you expected

  so to use TCP\ip you should send the packet length something like a header for your packet or 2 separated packet or as you like

  or as alternative for that to use delemited packets like streamreader or stream writer  if its text messages because it will be delemited by new line or you can design your own delemiter

  one more thing is to redeclair your array b4 every read or it will give you a headache as i told you

  2 days or even 2 months is not long while to learn sockets because its the most tricky thing i saw in .net

  there is a forum for networking http://forums.microsoft.com/MSDN/ShowForum.aspx ForumID=40&SiteID=1

  if you want this thread to be moved there tell me

  hope this helps

  
  
  

• PavanE

  Hi,

  Many thanks for your help again. What I think I've understood so far is that the "Connected" does not really handle if the socket is connected or not; I mean if the remote host disconnects, the "Connected" property of whatever else is not updated within the .Net socket handler...

  Here is a code I tried to translate from a java application which is working properly to VB.NET; I think this should work but (see below in red in the code): I've testing both java and VB.Net apps with a sniffer in order to check what is really happening

• owangecounty

  Hi,

  No problem for me to move in a more appropriate forum...

  The problem is that the application doesn't know what it will receive in advance: it can be structured with header as it cannot...

  I'm currently trying to build the application as a relay beteween Internet Explorer and a Web Server.

  Here is the code of my today's test:

  Dim ServerSocket As System.Net.Sockets.Socket = New System.Net.Sockets.Socket(Net.Sockets.AddressFamily.InterNetwork, Net.Sockets.SocketType.Stream, Net.Sockets.ProtocolType.Tcp)

  Dim ClientSocket As System.Net.Sockets.Socket = New System.Net.Sockets.Socket(Net.Sockets.AddressFamily.InterNetwork, Net.Sockets.SocketType.Stream, Net.Sockets.ProtocolType.Tcp)

  Dim LocalIPEndPoint As System.Net.IPEndPoint = New System.Net.IPEndPoint(System.Net.IPAddress.Loopback, 81)

  Dim Bytes() As Byte

  Dim AcceptSocket As System.Net.Sockets.Socket

  Dim S_NetStream As System.Net.Sockets.NetworkStream, C_NetStream As System.Net.Sockets.NetworkStream

  ServerSocket.Blocking = True

  ClientSocket.Blocking = True

  ServerSocket.Bind(LocalIPEndPoint)

  ServerSocket.Listen(10)

  Do

  AcceptSocket = ServerSocket.Accept()

  S_NetStream = New System.Net.Sockets.NetworkStream(AcceptSocket, True)

  S_NetStream.ReadTimeout = 5000

  S_NetStream.WriteTimeout = 5000

  ClientSocket.Connect("192.168.1.1", 80)

  C_NetStream = New System.Net.Sockets.NetworkStream(ClientSocket)

  C_NetStream.ReadTimeout = 5000

  C_NetStream.WriteTimeout = 5000

  If (ClientSocket.Connected = True) Then

  While ((AcceptSocket.Connected = True) And (ClientSocket.Connected = True))

  While (S_NetStream.DataAvailable = True) ON FIRST LOOP It is OK but in second loop it is not because there is no data anymore

  Bytes = new Byte(4096) {}

  S_NetStream.Read(Bytes, 0, Bytes.Length)

  C_NetStream.Write(Bytes, 0, Bytes.Length)

  If (C_NetStream.DataAvailable = True) Then

  Bytes = new Byte(4096) {}

  C_NetStream.Read(Bytes, 0, Bytes.Length)

  S_NetStream.Write(Bytes, 0, Bytes.Length)

  End If

  End While

  System.Threading.Thread.Sleep(50)

  End While

  End If

  C_NetStream.Close()

  C_NetStream.Dispose()

  S_NetStream.Close()

  S_NetStream.Dispose()

  ClientSocket.Close()

  Loop

  
  

• António João Carriço

  hi,

  ok make a break point and step over your code, and post the error message if there any or where does the application freez , one which line

  i still don't know why you put brackets around the array type "[byte]"

  best regards

  
  
  

• Moonracer

  Hi,

  Thanks for your help. I changed the code as you suggested.

  Now, the app does not return the error anymore but freezes in the first do/loop section after the second loop on SBytes = aSocket.Receive(sBuffer, 0, sBuffer.Length, Net.Sockets.SocketFlags.None)...

  It looks that aSocket.Receive does not return zero

   

  
  
• Newbie lost in socket programming with error "An existing connection was forcibly closed by the remote host"