WebSocket Development Guide

Table of Contents

• Overview
• Quick Start
• WebSocket Client
• WebSocket Server
• API Reference
• Event Reference
• Advanced Features
• FAQ

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Overview

WebSocket is a protocol for full-duplex communication over a single TCP connection. The new WebSocket library provides separated client and server implementations, supporting text and binary message transmission, with efficient buffer management and comprehensive error handling.

Key Features

• Separated Architecture - Independent implementations of client (cWebSocketClient) and server (cWebSocketServer)
• Protocol Support - Complete WebSocket protocol implementation (RFC 6455)
• Message Types - Supports both text and binary messages
• Frame Parser - cWebSocketFrame class dedicated to frame parsing and building
• Efficient Buffering - cByteBuffer class provides pre-allocation and auto-growth strategies
• Event-driven - Handles all network events through event mechanism
• Broadcasting - Server supports broadcasting messages to all clients

Project Structure

Websocket/
念岸岸 Client/
岫   念岸岸 frmClient.frm      # Client form
岫   念岸岸 WsClient.vbp       # Client project
岫   弩岸岸 WsClient.vbw
念岸岸 Server/
岫   念岸岸 frmServer.frm      # Server form
岫   念岸岸 WsServer.vbp       # Server project
岫   弩岸岸 WsServer.vbw
弩岸岸 README.md              # Example description

Library Architecture

newWebsocket/
念岸岸 mWebSocketUtils.bas           # Common utility module (UTF-8, Base64, SHA1, enum definitions)
念岸岸 cByteBuffer.cls               # High-performance byte buffer: pre-allocation, auto-growth, minimal memory operations
念岸岸 cWebSocketFrame.cls           # WebSocket frame parser: read-only parsing, separated unmask operations
念岸岸 cWebSocketClient.cls          # WebSocket client
念岸岸 cWebSocketServer.cls          # WebSocket server
弩岸岸 cWebSocketServerClient.cls    # Server client connection information

---

Quick Start

Requirements

• Visual Basic 6.0 or higher
• VBMAN.dll library (located in ..\..\..\vbman\dist\DLL\)

Reference Library

1. Open project WsClient.vbp or WsServer.vbp
2. Ensure VBMANLIB library is referenced
3. Check reference path: ..\..\..\vbman\dist\DLL\VBMAN.dll

Running the Example

1. Start Server

   • Open Server/WsServer.vbp
   • Run the project
   • Click "Start Service" button
   • Default listening port is 8080

2. Start Client

   • Open Client/WsClient.vbp
   • Run the project
   • Enter server address ws://127.0.0.1:8080
   • Click "Connect" button
   • Send messages after successful connection

3. Test Communication

   • Enter a message in the client and click "Send"
   • Server will echo the message
   • Sending "broadcast" will trigger server broadcast functionality

---

WebSocket Client

Creating a Client

Private WithEvents m_WsClient As cWebSocketClient

Private Sub InitializeClient()
    If m_WsClient Is Nothing Then
        Set m_WsClient = New cWebSocketClient
    End If
End Sub

Connecting to Server

Private Sub ConnectToServer(ByVal sURL As String)
    On Error GoTo EH
    
    InitializeClient()
    m_WsClient.Connect sURL
    
    LogMessage "Connecting to: " & sURL
    Exit Sub

EH:
    LogMessage "Connection failed: " & Err.Description
End Sub

Parameters:

• sURL: WebSocket server URL
  • Format: ws://host:port or wss://host:port (encrypted)
  • Example: ws://127.0.0.1:8080

Sending Text Message

Private Sub SendTextMessage(sMessage As String)
    On Error GoTo EH
    
    If Not m_WsClient Is Nothing And m_WsClient.State = WS_STATE_OPEN Then
        m_WsClient.SendText sMessage
        LogMessage "Sent: " & sMessage
    End If
    Exit Sub

EH:
    LogMessage "Send failed: " & Err.Description
End Sub

Sending Binary Message

Private Sub SendBinaryMessage(Data() As Byte)
    On Error GoTo EH
    
    If Not m_WsClient Is Nothing And m_WsClient.State = WS_STATE_OPEN Then
        m_WsClient.SendBinary Data
        LogMessage "Sent binary data: " & (UBound(Data) + 1) & " bytes"
    End If
    Exit Sub

EH:
    LogMessage "Send failed: " & Err.Description
End Sub

Sending Ping Frame

Private Sub SendPing(Optional Data() As Byte)
    On Error GoTo EH
    
    If Not m_WsClient Is Nothing And m_WsClient.State = WS_STATE_OPEN Then
        m_WsClient.Ping Data
        LogMessage "Ping sent"
    End If
    Exit Sub

EH:
    LogMessage "Ping send failed: " & Err.Description
End Sub

Disconnecting

Private Sub Disconnect(Optional ByVal Code As WsCloseCode = WS_CLOSE_NORMAL, Optional ByVal Reason As String = "")
    If Not m_WsClient Is Nothing Then
        m_WsClient.CloseConnection Code, Reason
        LogMessage "Disconnected"
    End If
End Sub

Close Code Description:

• WS_CLOSE_NORMAL (1000): Normal closure
• WS_CLOSE_GOING_AWAY (1001): Endpoint going away
• WS_CLOSE_PROTOCOL_ERROR (1002): Protocol error
• WS_CLOSE_UNSUPPORTED (1003): Unsupported data type
• WS_CLOSE_NO_STATUS (1005): No status code
• WS_CLOSE_ABNORMAL (1006): Abnormal closure
• WS_CLOSE_INVALID_PAYLOAD (1007): Invalid data
• WS_CLOSE_POLICY_VIOLATION (1008): Policy violation
• WS_CLOSE_MESSAGE_TOO_BIG (1009): Message too large
• WS_CLOSE_MANDATORY_EXT (1010): Mandatory extension missing
• WS_CLOSE_INTERNAL_ERROR (1011): Internal error
• WS_CLOSE_TLS_HANDSHAKE (1015): TLS handshake failed

Complete Example

Refer to Client/frmClient.frm file:

Private Sub cmdConnect_Click()
    On Error GoTo EH
    
    If m_WsClient Is Nothing Then
        Set m_WsClient = New cWebSocketClient
    End If
    
    m_WsClient.Connect txtURL.Text
    
    LogMessage "Connecting to: " & txtURL.Text
    cmdConnect.Enabled = False
    Exit Sub
EH:
    LogMessage "Connection failed: " & Err.Description
End Sub

Private Sub cmdSend_Click()
    On Error GoTo EH

    If Not m_WsClient Is Nothing And m_WsClient.State = WS_STATE_OPEN Then
        m_WsClient.SendText txtMessage.Text
        LogMessage "Sent: " & txtMessage.Text
    End If
    Exit Sub
EH:
    LogMessage "Send failed: " & Err.Description
End Sub

Private Sub UpdateUI(bConnected As Boolean)
    cmdConnect.Enabled = Not bConnected
    cmdDisconnect.Enabled = bConnected
    cmdSend.Enabled = bConnected
End Sub

---

WebSocket Server

Creating a Server

Private WithEvents m_WsServer As cWebSocketServer

Private Sub InitializeServer()
    If m_WsServer Is Nothing Then
        Set m_WsServer = New cWebSocketServer
    End If
End Sub

Starting to Listen

Private Sub StartServer(ByVal lPort As Long)
    On Error GoTo EH
    
    InitializeServer()
    m_WsServer.Listen lPort
    
    LogMessage "WebSocket server started, listening on port: " & lPort
    Exit Sub

EH:
    LogMessage "Service start failed: " & Err.Description
End Sub

Stopping Service

Private Sub StopServer()
    If Not m_WsServer Is Nothing Then
        m_WsServer.StopServer
        LogMessage "WebSocket server stopped"
    End If
End Sub

Sending Message to Specific Client

Private Sub SendToClient(ByVal ClientID As String, sMessage As String)
    On Error GoTo EH
    
    m_WsServer.SendText ClientID, sMessage
    LogMessage "Sent message to client " & ClientID & ": " & sMessage
    Exit Sub

EH:
    LogMessage "Send failed: " & Err.Description
End Sub

Sending Binary Message to Specific Client

Private Sub SendBinaryToClient(ByVal ClientID As String, Data() As Byte)
    On Error GoTo EH
    
    m_WsServer.SendBinary ClientID, Data
    LogMessage "Sent binary data to client " & ClientID & ": " & (UBound(Data) + 1) & " bytes"
    Exit Sub

EH:
    LogMessage "Send failed: " & Err.Description
End Sub

Broadcasting Message

Private Sub BroadcastMessage(sMessage As String, Optional ByVal ExcludeClientID As String = "")
    On Error GoTo EH
    
    m_WsServer.BroadcastText sMessage, ExcludeClientID
    LogMessage "Broadcast message: " & sMessage
    Exit Sub

EH:
    LogMessage "Broadcast failed: " & Err.Description
End Sub

Parameters:

• sMessage: Message to broadcast
• ExcludeClientID: Optional, client ID to exclude from broadcast (won't receive broadcast)

Broadcasting Binary Message

Private Sub BroadcastBinaryMessage(Data() As Byte, Optional ByVal ExcludeClientID As String = "")
    On Error GoTo EH
    
    m_WsServer.BroadcastBinary Data, ExcludeClientID
    LogMessage "Broadcast binary data: " & (UBound(Data) + 1) & " bytes"
    Exit Sub

EH:
    LogMessage "Broadcast failed: " & Err.Description
End Sub

Disconnecting Specific Client

Private Sub DisconnectClient(ByVal ClientID As String, Optional ByVal Code As WsCloseCode = WS_CLOSE_NORMAL, Optional ByVal Reason As String = "")
    On Error GoTo EH
    
    m_WsServer.DisconnectClient ClientID, Code, Reason
    LogMessage "Disconnected client " & ClientID
    Exit Sub

EH:
    LogMessage "Disconnect client failed: " & Err.Description
End Sub

Getting Client Information

Private Sub GetClientInfo(ByVal ClientID As String)
    Dim oClient As cWebSocketServerClient
    
    Set oClient = m_WsServer.GetClient(ClientID)
    
    If Not oClient Is Nothing Then
        LogMessage "Client ID: " & oClient.ID
        LogMessage "Remote Address: " & oClient.RemoteAddress
        LogMessage "Remote Port: " & oClient.RemotePort
        LogMessage "Connection Time: " & oClient.ConnectedTime
    End If
End Sub

Complete Example

Refer to Server/frmServer.frm file:

Private Sub cmdStart_Click()
    On Error GoTo EH

    If m_WsServer Is Nothing Then
        Set m_WsServer = New cWebSocketServer
    End If

    m_WsServer.Listen CLng(txtPort.Text)

    LogMessage "WebSocket server started, listening on port: " & txtPort.Text
    cmdStart.Enabled = False
    cmdStop.Enabled = True
    Exit Sub
EH:
    LogMessage "Service start failed: " & Err.Description
End Sub

Private Sub m_WsServer_OnClientTextMessage(ByVal ClientID As String, ByVal Message As String)
    LogMessage "Received text message from " & ClientID & ": " & Message

    ' Echo message
    m_WsServer.SendText ClientID, "Server received: " & Message

    ' If message is "broadcast", broadcast to all clients
    If LCase$(Message) = "broadcast" Then
        m_WsServer.BroadcastText "This is a broadcast message from client " & ClientID, ClientID
        LogMessage "Broadcast message sent to all clients"
    End If
End Sub

---

API Reference

cWebSocketClient Properties

Property	Type	Description
State	WsState	Connection state (see state constants)
URL	String	Connected WebSocket URL
ReadyState	WsState	ReadyState property (same as State)

cWebSocketClient Methods

Connect

m_WsClient.Connect URL

Connects to WebSocket server.

Parameters:

• URL: WebSocket server URL

SendText

m_WsClient.SendText Message

Sends text message.

Parameters:

• Message: Text message content

SendBinary

m_WsClient.SendBinary Data()

Sends binary message.

Parameters:

• Data: Byte array

Ping

m_WsClient.Ping [Data()]

Sends Ping frame.

Parameters:

• Data: Optional, additional data

CloseConnection

m_WsClient.CloseConnection [Code], [Reason]

Closes connection.

Parameters:

• Code: Optional, close code (default WS_CLOSE_NORMAL)
• Reason: Optional, close reason

cWebSocketServer Methods

Listen

m_WsServer.Listen Port

Starts listening on specified port.

Parameters:

• Port: Listening port number

StopServer

m_WsServer.StopServer

Stops service and disconnects all clients.

SendText

m_WsServer.SendText ClientID, Message

Sends text message to specified client.

Parameters:

• ClientID: Client ID
• Message: Text message content

SendBinary

m_WsServer.SendBinary ClientID, Data()

Sends binary message to specified client.

Parameters:

• ClientID: Client ID
• Data: Byte array

BroadcastText

m_WsServer.BroadcastText Message, [ExcludeClientID]

Broadcasts text message to all clients.

Parameters:

• Message: Text message content
• ExcludeClientID: Optional, client ID to exclude

BroadcastBinary

m_WsServer.BroadcastBinary Data(), [ExcludeClientID]

Broadcasts binary message to all clients.

Parameters:

• Data: Byte array
• ExcludeClientID: Optional, client ID to exclude

DisconnectClient

m_WsServer.DisconnectClient ClientID, [Code], [Reason]

Disconnects specified client.

Parameters:

• ClientID: Client ID
• Code: Optional, close code
• Reason: Optional, close reason

GetClient

Set oClient = m_WsServer.GetClient(ClientID)

Gets client object.

Parameters:

• ClientID: Client ID

Returns: cWebSocketServerClient object

State Constants

Constant	Value	Description
WS_STATE_CONNECTING	0	Connecting
WS_STATE_OPEN	1	Connected
WS_STATE_CLOSING	2	Closing
WS_STATE_CLOSED	3	Closed

---

Event Reference

Client Events

OnOpen

Private Sub m_WsClient_OnOpen()

Triggered when connection is successfully established.

OnClose

Private Sub m_WsClient_OnClose(ByVal Code As WsCloseCode, ByVal Reason As String)

Triggered when connection is closed.

Parameters:

• Code: Close code
• Reason: Close reason

OnTextMessage

Private Sub m_WsClient_OnTextMessage(ByVal Message As String)

Triggered when text message is received.

Parameters:

• Message: Text message content

OnBinaryMessage

Private Sub m_WsClient_OnBinaryMessage(Data() As Byte)

Triggered when binary message is received.

Parameters:

• Data: Binary data array

OnError

Private Sub m_WsClient_OnError(ByVal Description As String)

Triggered when an error occurs.

Parameters:

• Description: Error description

OnPong

Private Sub m_WsClient_OnPong(Data() As Byte)

Triggered when Pong response is received.

Parameters:

• Data: Pong data

Server Events

OnStart

Private Sub m_WsServer_OnStart(ByVal Port As Long)

Triggered when service starts.

Parameters:

• Port: Listening port number

OnStop

Private Sub m_WsServer_OnStop()

Triggered when service stops.

OnClientConnect

Private Sub m_WsServer_OnClientConnect(ByVal ClientID As String, ByVal RemoteAddress As String, ByVal RemotePort As Long)

Triggered when new client connects.

Parameters:

• ClientID: Client ID
• RemoteAddress: Client IP address
• RemotePort: Client port

OnClientDisconnect

Private Sub m_WsServer_OnClientDisconnect(ByVal ClientID As String, ByVal Reason As String)

Triggered when client disconnects.

Parameters:

• ClientID: Client ID
• Reason: Disconnect reason

OnClientTextMessage

Private Sub m_WsServer_OnClientTextMessage(ByVal ClientID As String, ByVal Message As String)

Triggered when text message is received from client.

Parameters:

• ClientID: Client ID
• Message: Text message content

OnClientBinaryMessage

Private Sub m_WsServer_OnClientBinaryMessage(ByVal ClientID As String, Data() As Byte)

Triggered when binary message is received from client.

Parameters:

• ClientID: Client ID
• Data: Binary data array

OnError

Private Sub m_WsServer_OnError(ByVal Description As String)

Triggered when an error occurs.

Parameters:

• Description: Error description

---

Advanced Features

Client Auto-reconnect

Implement client auto-reconnection mechanism:

Private WithEvents tmrReconnect As Timer
Private lReconnectAttempts As Long

Private Sub m_WsClient_OnClose(ByVal Code As WsCloseCode, ByVal Reason As String)
    LogMessage "Connection closed: " & Reason
    
    ' Attempt reconnection on abnormal close
    If Code <> WS_CLOSE_NORMAL Then
        StartReconnectTimer
    End If
End Sub

Private Sub StartReconnectTimer()
    lReconnectAttempts = 0
    Set tmrReconnect = New Timer
    tmrReconnect.Interval = 3000  ' Reconnect after 3 seconds
    tmrReconnect.Enabled = True
End Sub

Private Sub tmrReconnect_Timer()
    tmrReconnect.Enabled = False
    
    If lReconnectAttempts < 5 Then
        lReconnectAttempts = lReconnectAttempts + 1
        LogMessage "Attempting to reconnect (" & lReconnectAttempts & "/5)..."
        m_WsClient.Connect txtURL.Text
    Else
        LogMessage "Reconnection failed, maximum attempts reached"
    End If
End Sub

Heartbeat Keep-alive

Implement heartbeat keep-alive for both client and server:

' Client side
Private WithEvents tmrHeartbeat As Timer

Private Sub m_WsClient_OnOpen()
    LogMessage "Connected, starting heartbeat"
    
    Set tmrHeartbeat = New Timer
    tmrHeartbeat.Interval = 30000  ' 30 seconds
    tmrHeartbeat.Enabled = True
End Sub

Private Sub tmrHeartbeat_Timer()
    If m_WsClient.State = WS_STATE_OPEN Then
        m_WsClient.Ping
        LogMessage "Heartbeat Ping sent"
    End If
End Sub

' Server side - record last activity time
Private Sub m_WsServer_OnClientTextMessage(ByVal ClientID As String, ByVal Message As String)
    ' Record client activity time
    Dim oClient As cWebSocketServerClient
    Set oClient = m_WsServer.GetClient(ClientID)
    If Not oClient Is Nothing Then
        oClient.LastActivity = Now
    End If
End Sub

Message Queue

Implement message queue to ensure message order:

Private colMessageQueue As Collection
Private bSending As Boolean

Private Sub InitializeQueue()
    Set colMessageQueue = New Collection
    bSending = False
End Sub

Private Sub EnqueueMessage(sMessage As String)
    colMessageQueue.Add sMessage
    
    If Not bSending Then
        ProcessQueue
    End If
End Sub

Private Sub ProcessQueue()
    If colMessageQueue.Count > 0 And m_WsClient.State = WS_STATE_OPEN Then
        bSending = True
        
        ' Get first message from queue
        Dim sMessage As String
        sMessage = colMessageQueue(1)
        colMessageQueue.Remove 1
        
        ' Send message
        m_WsClient.SendText sMessage
    Else
        bSending = False
    End If
End Sub

Private Sub m_WsClient_OnTextMessage(ByVal Message As String)
    LogMessage "Received response: " & Message
    
    ' Process next message
    If colMessageQueue.Count > 0 Then
        ProcessQueue
    Else
        bSending = False
    End If
End Sub

Authentication Mechanism

Implement simple token authentication:

' Server - validate on connection
Private Sub m_WsServer_OnClientConnect(ByVal ClientID As String, ByVal RemoteAddress As String, ByVal RemotePort As Long)
    Dim oClient As cWebSocketServerClient
    Set oClient = m_WsServer.GetClient(ClientID)
    
    ' Check token in query parameters
    Dim sToken As String
    sToken = ExtractTokenFromClient(oClient)
    
    If Not IsValidToken(sToken) Then
        LogMessage "Authentication failed, disconnecting client: " & ClientID
        m_WsServer.DisconnectClient ClientID, WS_CLOSE_POLICY_VIOLATION, "Invalid token"
        Exit Sub
    End If
    
    LogMessage "Client authenticated successfully: " & ClientID
End Sub

' Client - attach token in URL
Private Sub ConnectWithToken(ByVal sURL As String, ByVal sToken As String)
    Dim sURLWithToken As String
    sURLWithToken = sURL & "?token=" & sToken
    
    m_WsClient.Connect sURLWithToken
End Sub

Message Compression

Use Deflate algorithm to compress messages:

Private Sub SendCompressedMessage(sMessage As String)
    Dim byOriginal() As Byte
    Dim byCompressed() As Byte
    
    ' Convert to UTF-8 byte array
    byOriginal = UTF8.GetBytes(sMessage)
    
    ' Compress data (need to implement Deflate compression function)
    byCompressed = CompressData(byOriginal)
    
    ' Send compressed data
    m_WsClient.SendBinary byCompressed
    LogMessage "Sent compressed message: " & (UBound(byOriginal) + 1) & " -> " & (UBound(byCompressed) + 1) & " bytes"
End Sub

---

FAQ

Q1: How to handle connection timeout?

A: Use a timer to monitor connection state:

Private WithEvents tmrConnect As Timer

Private Sub StartConnectTimer()
    Set tmrConnect = New Timer
    tmrConnect.Interval = 10000  ' 10 second timeout
    tmrConnect.Enabled = True
End Sub

Private Sub tmrConnect_Timer()
    tmrConnect.Enabled = False
    
    If m_WsClient.State = WS_STATE_CONNECTING Then
        LogMessage "Connection timeout"
        m_WsClient.CloseConnection WS_CLOSE_ABNORMAL, "Connection timeout"
        UpdateUI False
    End If
End Sub

Private Sub m_WsClient_OnOpen()
    tmrConnect.Enabled = False
    LogMessage "Connection successful"
End Sub

Q2: How to handle large messages?

A: Use message chunking:

Private Sub SendLargeMessage(sMessage As String)
    Const MAX_CHUNK_SIZE As Long = 1024  ' 1KB chunk
    Dim lLength As Long
    Dim lOffset As Long
    Dim sChunk As String
    
    lLength = Len(sMessage)
    lOffset = 1
    
    Do While lOffset <= lLength
        sChunk = Mid(sMessage, lOffset, MAX_CHUNK_SIZE)
        m_WsClient.SendText sChunk
        
        LogMessage "Sent chunk " & (lOffset \ MAX_CHUNK_SIZE + 1) & ": " & Len(sChunk) & " bytes"
        lOffset = lOffset + MAX_CHUNK_SIZE
        
        ' Short delay
        DoEvents
        Sleep 50
    Loop
End Sub

Q3: How to limit client connections?

A: Maintain client count on server:

Private lMaxClients As Long
Private lCurrentClients As Long

Private Sub InitializeServer()
    lMaxClients = 100  ' Maximum client count
    lCurrentClients = 0
End Sub

Private Sub m_WsServer_OnClientConnect(ByVal ClientID As String, ByVal RemoteAddress As String, ByVal RemotePort As Long)
    If lCurrentClients >= lMaxClients Then
        LogMessage "Connection rejected: maximum client count reached"
        m_WsServer.DisconnectClient ClientID, WS_CLOSE_TRY_AGAIN_LATER, "Server full"
        Exit Sub
    End If
    
    lCurrentClients = lCurrentClients + 1
    LogMessage "Client connection: " & ClientID & " (current: " & lCurrentClients & "/" & lMaxClients & ")"
End Sub

Private Sub m_WsServer_OnClientDisconnect(ByVal ClientID As String, ByVal Reason As String)
    lCurrentClients = lCurrentClients - 1
    LogMessage "Client disconnect: " & ClientID & " (current: " & lCurrentClients & ")"
End Sub

Q4: How to implement room functionality?

A: Use client grouping:

Private colRooms As Collection

Private Sub InitializeRooms()
    Set colRooms = New Collection
End Sub

' Join room
Private Sub JoinRoom(ByVal ClientID As String, ByVal sRoom As String)
    Dim colClients As Collection
    
    On Error Resume Next
    Set colClients = colRooms(sRoom)
    
    If colClients Is Nothing Then
        Set colClients = New Collection
        colRooms.Add colClients, sRoom
    End If
    
    On Error GoTo 0
    colClients.Add ClientID, ClientID
    LogMessage "Client " & ClientID & " joined room: " & sRoom
End Sub

' Send to room
Private Sub SendToRoom(ByVal sRoom As String, ByVal sMessage As String)
    Dim colClients As Collection
    Dim i As Long
    
    On Error Resume Next
    Set colClients = colRooms(sRoom)
    On Error GoTo 0
    
    If Not colClients Is Nothing Then
        For i = 1 To colClients.Count
            m_WsServer.SendText colClients(i), sMessage
        Next i
    End If
End Sub

Q5: How to debug WebSocket communication?

A: Record all events and detailed logs:

Private Sub LogWebSocketEvent(ByVal sEventType As String, ByVal sDetails As String)
    Dim sLog As String
    sLog = Format$(Now, "yyyy-mm-dd hh:mm:ss") & " [" & sEventType & "] " & sDetails
    
    ' Output to log window
    txtLog.Text = txtLog.Text & sLog & vbCrLf
    txtLog.SelStart = Len(txtLog.Text)
    
    ' Output to debug window
    Debug.Print sLog
    
    ' Optional: write to file
    LogToFile sLog
End Sub

Private Sub LogToFile(sLog As String)
    Dim nFile As Integer
    nFile = FreeFile
    
    Open App.Path & "\websocket.log" For Append As #nFile
    Print #nFile, sLog
    Close #nFile
End Sub

---

Best Practices

1. Resource cleanup: Call CloseConnection or StopServer when form unloads to release resources
2. Error handling: Include error handling for all network operations
3. State checking: Check State = WS_STATE_OPEN before sending messages
4. Logging: Record key events for easier debugging and troubleshooting
5. Timeout handling: Implement reasonable connection and operation timeouts
6. Heartbeat keep-alive: Periodically send Ping frames to keep connection active
7. Message validation: Validate format and length when receiving messages
8. Graceful shutdown: Use correct close codes and reason information
9. Client limiting: Implement reasonable client connection limits
10. Security authentication: Implement authentication mechanisms in production environments

---

Protocol Specification

WebSocket Handshake Process

1. Client Request

GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Version: 13

2. Server Response

HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=

Frame Structure

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-------+-+-------------+-------------------------------+
|F|R|R|R| opcode|M| Payload len |    Extended payload length    |
|I|S|S|S|  (4)  |A|     (7)     |             (16/64)           |
|N|V|V|V|       |S|             |   (if payload len==126/127)   |
| |1|2|3|       |K|             |                               |
+-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
|     Extended payload length continued, if payload len == 127  |
+ - - - - - - - - - - - - - - - +-------------------------------+
|                               |Masking-key, if MASK set to 1  |
+-------------------------------+-------------------------------+
| Masking-key (continued)       |           Payload Data         |
+-------------------------------- - - - - - - - - - - - - - - - +
:                     Payload Data continued ...                :
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
|                     Payload Data continued ...                |
+---------------------------------------------------------------+

Opcodes

Value	Description
0x0	Continuation frame
0x1	Text frame
0x2	Binary frame
0x8	Close frame
0x9	Ping frame
0xA	Pong frame

---

Related Resources

• Project directory: Websocket/
• Client example: Client/frmClient.frm
• Server example: Server/frmServer.frm
• Dependency library: VBMAN.dll
• WebSocket Protocol: RFC 6455

---

Changelog

• v2.0 - New library version, separated client/server, optimized architecture
  • Separated client (cWebSocketClient) and server (cWebSocketServer) classes
  • Independent frame parser (cWebSocketFrame)
  • Efficient buffer management (cByteBuffer)
  • Clear separation of concerns and error handling
• v1.0 - Initial version