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POVB.NET - Data from TCP Client isn't in order
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copied!<p>I've been working on this project for about a year now. It's a basic client\server chat program. After a long time of improvement, I decided to test out the strength of my server.</p> <p>On the client, I fired off 200 chat messages ("FLOOD# 1"... "FLOOD# 200") to the server as fast as possible. The result: Server immediately crashes. After some slight tampering, I was able to get the server to process 135 of the 200 messages before giving up. It no longer crashes, but something different happens. The data from the client is received in order, but when I pass that message to a function (<em>myForm.OnLineReceived</em>), The data is completely out of order. If I add a slight delay between the calling of the OnLineRecieved function, The messages are in perfect order.</p> <p>Each message from the client is first encrypted, then encoded in base64. An "-" is appended to the end so that the server can easily find the end of each data "packet".</p> <p>I'm sure that it's some stupid mistake that you guys will easily find and point out to me. Thanks for taking a look ;)</p> <h2>Server Code:</h2> <pre><code>Imports System.Net.Sockets Imports System.Text ' The UserConnection class encapsulates the functionality of a TcpClient connection ' with streaming for a single user. Public Class UserConnection Private client As TcpClient Private readBuffer(READ_BUFFER_SIZE) As Byte Public UID As String = "" Public isAdmin As Boolean Public IpAddress As String Public username As String = "" Public Country As String = "" Public ServerID As String = "" Public Status As String = "" Public UserComp As String = "" Public OS As String = "" Public SessionKey As String = "" Public UsePublicKeyEncryption As Boolean = True Public Version As Decimal = 0.0 Const READ_BUFFER_SIZE As Integer = 500 Private _commands As New System.Text.StringBuilder Private command_count As Integer = 1 ' Overload the New operator to set up a read thread. Public Sub New(ByVal client As TcpClient) 'this runs every time a new client is added Me.client = client IpAddress = Me.client.Client.RemoteEndPoint.ToString.Substring(0, Me.client.Client.RemoteEndPoint.ToString.LastIndexOf(":")) 'ip address of client ' This starts the asynchronous read thread. The data will be saved into ' readBuffer. Call Worker() End Sub Public Sub ForceKill() On Error Resume Next client.GetStream.Close() client.Close() client = Nothing End Sub Private Sub Worker() Try SyncLock client Dim tmp_byte(client.ReceiveBufferSize) As Byte Me.client.GetStream.BeginRead(tmp_byte, 0, client.ReceiveBufferSize, AddressOf RecieveDataAndSplit, Nothing) readBuffer = tmp_byte End SyncLock Catch Call myForm.OnLineReceived(Me, "D") 'this also calls ForceKill() End Try End Sub Public Event LineReceived(ByVal sender As UserConnection, ByVal Data As String) ' This subroutine uses a StreamWriter to send a message to the user. Public Sub SendData(ByVal Data As String) ' Synclock ensure that no other threads try to use the stream at the same time. SyncLock client Dim writer As New IO.StreamWriter(client.GetStream) writer.Write(ToBase64(AES_Encrypt(Data, SessionKey)) & "-") ' Make sure all data is sent now. writer.Flush() End SyncLock End Sub Public Sub RecieveDataAndSplit(ByVal ar As IAsyncResult) 'this is the FIRST function that incoming data is ran through Dim BytesRead As Integer Dim Content As String Try ' Ensure that no other threads try to use the stream at the same time. SyncLock client ' Finish asynchronous read into readBuffer and get number of bytes read. BytesRead = client.GetStream.EndRead(ar) End SyncLock Catch e As Exception Call myForm.OnLineReceived(Me, "D") 'couldn't read the stream from the client. Kill our connection with them :P Exit Sub End Try Try Content = Encoding.ASCII.GetString(readBuffer, 0, BytesRead) Catch ex As Exception Call Worker() Exit Sub End Try Dim commands() As String Try commands = LineTrim(Content).Split("-") Catch End Try Dim i As Integer = 0 For i = 0 To commands.Length - 1 If commands(i) <> "" Then Dim decrypted_content As String = AES_Decrypt(FromBase64(commands(i)), SessionKey) If decrypted_content <> "" Then 'If decrypted_content = "D" Or Nothing Then ' client.GetStream.Close() ' client.Close() ' Call myForm.OnLineReceived(Me, decrypted_content) 'Else Call myForm.OnLineReceived(Me, decrypted_content) Call Worker() 'reads the stream again 'End If End If End If Next End Sub End Class </code></pre> <hr> <h2>Client Code:</h2> <pre><code>Public Sub SendData(ByVal data As String) Try If data = "D" Then 'telling server that we're closing ForceDisconnect(False) Else 'any other message Dim sendBytes As [Byte]() sendBytes = Encoding.ASCII.GetBytes(ToBase64(AES_Encrypt(data, SessionKey)) & "-") Dim networkStream As NetworkStream = tcp_client.GetStream() networkStream.Write(sendBytes, 0, sendBytes.Length) networkStream.Flush() End If Catch ex As Exception connection_state_toggle(False) Label1.ForeColor = Color.Black Label1.Text = "Idle" End Try End Sub </code></pre>

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