Draft
This page is not complete.
The following sample is not optimized. It does not make use of .NET 4.5 Websocket support.
The current version:
- contains A Generic Collection of a class that wraps System.Net.Sockets.TcpClient
- features Custom Events and Delegate Handlers
- features Threading and implements Timers.Timer
- demonstrates how to write a frame back to the client using the Network Stream (opCode 0001)
- is intended to be a starting point for this tutorial and for other contributors
Imports System.Net.Sockets
Imports System.Net
Imports System
Imports System.Text
Imports System.Text.RegularExpressions
Namespace TypeDef.WebSocket
Public Class Client
Dim _TcpClient As System.Net.Sockets.TcpClient
Public Delegate Sub OnClientDisconnectDelegateHandler()
Public Event onClientDisconnect As OnClientDisconnectDelegateHandler
Sub New(ByVal tcpClient As System.Net.Sockets.TcpClient)
Me._TcpClient = tcpClient
End Sub
Function isConnected() As Boolean
Return Me._TcpClient.Connected
End Function
Sub HandShake()
Dim stream As NetworkStream = Me._TcpClient.GetStream()
Dim bytes As Byte()
Dim data As String
While Me._TcpClient.Connected
While (stream.DataAvailable)
ReDim bytes(Me._TcpClient.Client.Available)
stream.Read(bytes, 0, bytes.Length)
data = System.Text.Encoding.UTF8.GetString(bytes)
If (New System.Text.RegularExpressions.Regex("^GET").IsMatch(data)) Then
Dim response As Byte() = System.Text.Encoding.UTF8.GetBytes("HTTP/1.1 101 Switching Protocols" & Environment.NewLine & "Connection: Upgrade" & Environment.NewLine & "Upgrade: websocket" & Environment.NewLine & "Sec-WebSocket-Accept: " & Convert.ToBase64String(System.Security.Cryptography.SHA1.Create().ComputeHash(Encoding.UTF8.GetBytes(New Regex("Sec-WebSocket-Key: (.*)").Match(data).Groups(1).Value.Trim() & "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"))) & Environment.NewLine & Environment.NewLine)
stream.Write(response, 0, response.Length)
Exit Sub
Else
'We're going to disconnect the client here, because he's not handshacking properly (or at least to the scope of this code sample)
Me._TcpClient.Close() 'The next While Me._TcpClient.Connected Loop Check should fail.. and raise the onClientDisconnect Event Thereafter
End If
End While
End While
RaiseEvent onClientDisconnect()
End Sub
Sub CheckForDataAvailability()
If (Me._TcpClient.GetStream().DataAvailable) Then
Dim stream As NetworkStream = Me._TcpClient.GetStream()
Dim frameCount = 2
Dim bytes As Byte()
Dim data As String
ReDim bytes(Me._TcpClient.Client.Available)
stream.Read(bytes, 0, bytes.Length) 'Read the stream, don't close it..
Try
Dim length As UInteger = bytes(1) - 128 'this should obviously be a byte (unsigned 8bit value)
If length > -1 Then
If length = 126 Then
length = 4
ElseIf length = 127 Then
length = 10
End If
End If
'the following is very inefficient and likely unnecessary..
'the main purpose is to just get the lower 4 bits of byte(0) - which is the OPCODE
Dim value As Integer = bytes(0)
Dim bitArray As BitArray = New BitArray(8)
For c As Integer = 0 To 7 Step 1
If value - (2 ^ (7 - c)) >= 0 Then
bitArray.Item(c) = True
value -= (2 ^ (7 - c))
Else
bitArray.Item(c) = False
End If
Next
Dim FRRR_OPCODE As String = ""
For Each bit As Boolean In bitArray
If bit Then
FRRR_OPCODE &= "1"
Else
FRRR_OPCODE &= "0"
End If
Next
Dim FIN As Integer = FRRR_OPCODE.Substring(0, 1)
Dim RSV1 As Integer = FRRR_OPCODE.Substring(1, 1)
Dim RSV2 As Integer = FRRR_OPCODE.Substring(2, 1)
Dim RSV3 As Integer = FRRR_OPCODE.Substring(3, 1)
Dim opCode As Integer = Convert.ToInt32(FRRR_OPCODE.Substring(4, 4), 2)
Dim decoded(bytes.Length - (frameCount + 4)) As Byte
Dim key As Byte() = {bytes(frameCount), bytes(frameCount+1), bytes(frameCount+2), bytes(frameCount+3)}
Dim j As Integer = 0
For i As Integer = (frameCount + 4) To (bytes.Length - 2) Step 1
decoded(j) = Convert.ToByte((bytes(i) Xor masks(j Mod 4)))
j += 1
Next
Select Case opCode
Case Is = 1
'Text Data Sent From Client
data = System.Text.Encoding.UTF8.GetString(decoded)
'handle this data
Dim Payload As Byte() = System.Text.Encoding.UTF8.GetBytes("Text Recieved")
Dim FRRROPCODE As Byte() = Convert.ToByte("10000001", 2) 'FIN is set, and OPCODE is 1 or Text
Dim header as byte() = {FRRROPCODE, Convert.ToByte(Payload.Length)}
Dim ResponseData As Byte()
ReDim ResponseData((header.length + Payload.Length) - 1)
'NOTEWORTHY: if you Redim ResponseData(header.length + Payload.Length).. you'll add a 0 value byte at the end of the response data..
'which tells the client that your next stream write will be a continuation frame..
Dim index as integer = 0
Buffer.BlockCopy(header, 0, ResponseData, index, header.length)
index += header.length
Buffer.BlockCopy(payload, 0, ResponseData, index, payload.length)
index += payload.length
stream.Write(ResponseData, 0, ResponseData.Length)
Case Is = 2
'// Binary Data Sent From Client
data = System.Text.Encoding.UTF8.GetString(decoded)
Dim response As Byte() = System.Text.Encoding.UTF8.GetBytes("Binary Recieved")
stream.Write(response, 0, response.Length)
Case Is = 9 '// Ping Sent From Client
Case Is = 10 '// Pong Sent From Client
Case Else '// Improper opCode.. disconnect the client
_TcpClient.Close()
RaiseEvent onClientDisconnect()
End Select
Catch ex As Exception
_TcpClient.Close()
RaiseEvent onClientDisconnect()
End Try
End If
End Sub
End Class
Public Class Server
Inherits System.Net.Sockets.TcpListener
Delegate Sub OnClientConnectDelegate(ByVal sender As Object, ByRef Client As WebSocket.Client)
Event OnClientConnect As OnClientConnectDelegate
Dim WithEvents PendingCheckTimer As Timers.Timer = New Timers.Timer(500)
Dim WithEvents ClientDataAvailableTimer As Timers.Timer = New Timers.Timer(50)
Property ClientCollection As List(Of WebSocket.Client) = New List(Of WebSocket.Client)
Sub New(ByVal url As String, ByVal port As Integer)
MyBase.New(IPAddress.Parse(url), port)
End Sub
Sub startServer()
Me.Start()
PendingCheckTimer.Start()
End Sub
Sub Client_Connected(ByVal sender As Object, ByRef client As WebSocket.Client) Handles Me.OnClientConnect
Me.ClientCollection.Add(client)
AddHandler client.onClientDisconnect, AddressOf Client_Disconnected
client.HandShake()
ClientDataAvailableTimer.Start()
End Sub
Sub Client_Disconnected()
End Sub
Function isClientDisconnected(ByVal client As WebSocket.Client) As Boolean
isClientDisconnected = False
If Not client.isConnected Then
Return True
End If
End Function
Function isClientConnected(ByVal client As WebSocket.Client) As Boolean
isClientConnected = False
If client.isConnected Then
Return True
End If
End Function
Private Sub PendingCheckTimer_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs) Handles PendingCheckTimer.Elapsed
If Pending() Then
RaiseEvent OnClientConnect(Me, New CORE.TypeDef.WebSocket.Client(Me.AcceptTcpClient()))
End If
End Sub
Private Sub ClientDataAvailableTimer_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs) Handles ClientDataAvailableTimer.Elapsed
Me.ClientCollection.RemoveAll(AddressOf isClientDisconnected)
If Me.ClientCollection.Count < 1 Then ClientDataAvailableTimer.Stop()
For Each Client As WebSocket.Client In Me.ClientCollection
Client.CheckForDataAvailability()
Next
End Sub
End Class
End Namespace
Sub Main() 'Program Entry point
Dim thread As System.Threading.Thread = New System.Threading.Thread(AddressOf StartWebSocketServer)
'Application.Add("WebSocketServerThread", thread) 'Global.asax - context.Application .. I left this part in for web application developers
thread.Start()
End Sub
Public Shared WebSocketServer As TypeDef.WebSocket.Server
Public Shared Sub StartWebSocketServer()
WebSocketServer = New TypeDef.WebSocket.Server("127.0.0.1", 8000)
WebSocketServer.startServer()
End Sub