cWinsock Methods Reference

📋 Method List

Method Name	Return Type	Description
Connect	Sub	Connect to remote server
Listen	Sub	Start listening on port
Bind	Sub	Bind local port (UDP)
SendData	Sub	Send data
GetData	Sub	Receive data
PeekData	Sub	Peek at data without removing
Close_	Sub	Close connection
GetErrorDescription	String	Get error description
AcceptFrom	Sub	Accept connection (internal method)
SetUdpClientInfo	Sub	Set UDP client info (internal method)
RemoveClient	Sub	Remove client (internal method)
RaiseDataArrivalEvent	Sub	Trigger data arrival event (internal method)

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🔗 Connect Method

Description

Connect to the specified remote server (TCP client mode).

Syntax

Public Sub Connect(Optional RemoteHost As String, Optional ByVal RemotePort As Long)

Parameters

Parameter	Type	Description
RemoteHost	String (optional)	Remote hostname or IP address. If not provided, uses RemoteHost property value
RemotePort	Long (optional)	Remote port number. If not provided, uses RemotePort property value

Usage Example

' Connect using parameters
m_oClient.Connect "127.0.0.1", 8080

' Connect using properties
m_oClient.RemoteHost = "example.com"
m_oClient.RemotePort = 80
m_oClient.Connect

' Connect to specific host
m_oClient.RemoteHost = "192.168.1.100"
m_oClient.Connect , 8080  ' Only specify port, use already set RemoteHost

Connection Flow

1. Call Connect()
2. Close existing connection (if any)
3. Resolve hostname → sckResolvingHost
4. Hostname resolved → sckHostResolved
5. Start connecting → sckConnecting
6. Connection successful → sckConnected
7. Trigger Connect event

Error Handling

Private Sub cmdConnect_Click()
    On Error GoTo EH
    
    m_oClient.Connect "example.com", 8080
    Exit Sub
    
EH:
    Debug.Print "Connection error: " & Err.Description
    Select Case Err.Number
        Case 10060
            MsgBox "Connection timeout, please check network"
        Case 10061
            MsgBox "Server refused connection, please check port"
        Case Else
            MsgBox "Connection failed: " & Err.Description
    End Select
End Sub

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🎧 Listen Method

Description

Start listening on the specified port, waiting for client connections (TCP server mode).

Syntax

Public Sub Listen(Optional ByVal Port As Long)

Parameters

Parameter	Type	Description
Port	Long (optional)	Port number to listen on. If not provided, uses LocalPort property value

Usage Example

' Listen using parameter
m_oServer.Listen 8080

' Listen using property
m_oServer.LocalPort = 8080
m_oServer.Listen

' Listen on multiple ports (need multiple cWinsock objects)
Dim oServer1 As New cWinsock
Dim oServer2 As New cWinsock
oServer1.Listen 8080
oServer2.Listen 8081

Server Startup Flow

Private Sub StartServer()
    On Error GoTo EH
    
    ' Set protocol
    m_oServer.Protocol = sckTCPProtocol
    
    ' Start listening
    m_oServer.Listen 8080
    
    Debug.Print "Server started, listening on port: " & m_oServer.LocalPort
    
    ' Update UI
    btnStart.Enabled = False
    btnStop.Enabled = True
    lblStatus.Caption = "Listening..."
    
    Exit Sub
    
EH:
    Debug.Print "Failed to start server: " & Err.Description
    MsgBox "Cannot start server: " & Err.Description, vbExclamation
End Sub

⚠️ Notes

• Must set Protocol = sckTCPProtocol before calling Listen()
• Port must not be already in use
• State will become sckListening

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📌 Bind Method

Description

Bind to local port (UDP server mode).

Syntax

Public Sub Bind(Optional ByVal LocalPort As Long, Optional LocalIP As String)

Parameters

Parameter	Type	Description
LocalPort	Long (optional)	Local port number to bind
LocalIP	String (optional)	Local IP address to bind (optional)

Usage Example

' Bind port
m_oUdp.Protocol = sckUDPProtocol
m_oUdp.Bind 8888

' Bind to specific IP
m_oUdp.Bind 8888, "192.168.1.100"

UDP Server Startup

Private Sub StartUdpServer()
    On Error GoTo EH
    
    ' Set protocol
    m_oUdp.Protocol = sckUDPProtocol
    
    ' Bind port
    m_oUdp.Bind 8888
    
    Debug.Print "UDP server started, bound to port: " & m_oUdp.LocalPort
    
    Exit Sub
    
EH:
    Debug.Print "UDP bind failed: " & Err.Description
    MsgBox "Cannot bind UDP port: " & Err.Description, vbExclamation
End Sub

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📤 SendData Method

Description

Send data to remote host.

Syntax

Public Sub SendData(Data As Variant, Optional ByVal CodePage As EnumScpCodePage = ScpAcp)

Parameters

Parameter	Type	Description
Data	Variant	Data to send, can be string or byte array
CodePage	EnumScpCodePage (optional)	Text encoding, default ScpAcp (GBK/ACP)

Encoding Options

Constant	Value	Description
ScpAcp	0	System default code page (GBK on Chinese Windows)
ScpOem	1	OEM code page
ScpUtf8	65001	UTF-8 encoding
ScpUnicode	-1	Unicode, no encoding conversion

Sending String

' Default uses ACP/GBK encoding
m_oClient.SendData "中文测试"

' Use UTF-8 encoding
m_oClient.SendData "中文测试", ScpUtf8

' Use Unicode (no conversion)
m_oClient.SendData "中文测试", ScpUnicode

Sending Byte Array

' Send byte array
Dim baData() As Byte
baData = GetBinaryData()
m_oClient.SendData baData

UDP Server Sending

' In UDP server mode, need to specify remote address
Private Sub cmdUdpSend_Click()
    ' Set target
    m_oUdp.RemoteHost = "127.0.0.1"
    m_oUdp.RemotePort = 9999
    
    ' Send data
    m_oUdp.SendData "Hello, UDP!"
End Sub

' Reply to specific client (virtual client)
Private Sub m_oUdp_DataArrival(Client As cWinsock, ByVal bytesTotal As Long)
    Dim sData As String
    Client.GetData sData
    
    ' Reply directly through Client object
    ' cWinsock automatically uses correct remote address:port
    Client.SendData "Reply: " & sData
End Sub

Large Data Sending

' Send large data in chunks
Private Sub SendLargeFile(ByVal sFilePath As String)
    Dim baChunk() As Byte
    Dim lChunkSize As Long
    lChunkSize = 8192 ' 8KB per chunk
    
    ' Open file...
    ' Loop read and send
    Do While Not EOF
        ' Read data chunk
        ReadChunk baChunk, lChunkSize
        
        ' Send
        m_oClient.SendData baChunk
        
        ' Wait for send completion (via SendComplete event)
        Do While m_bSending
            DoEvents
        Loop
    Loop
End Sub

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📥 GetData Method

Description

Read data from receive buffer.

Syntax

Public Sub GetData(Data As Variant, Optional ByVal VarType_ As Long, Optional ByVal MaxLen As Long = -1, Optional ByVal CodePage As EnumScpCodePage = ScpAcp)

Parameters

Parameter	Type	Description
Data	Variant	Variable to receive data
VarType_	Long (optional)	Expected data type (e.g., vbString, vbByte + vbArray)
MaxLen	Long (optional)	Maximum bytes to read, -1 means read all
CodePage	EnumScpCodePage (optional)	Text encoding, default ScpAcp

Reading String

Private Sub m_oClient_DataArrival(Client As cWinsock, ByVal bytesTotal As Long)
    Dim sData As String
    
    ' Read all data
    Client.GetData sData
    
    Debug.Print "Received: " & sData
End Sub

Reading Byte Array

Private Sub m_oClient_DataArrival(Client As cWinsock, ByVal bytesTotal As Long)
    Dim baData() As Byte
    
    ' Read byte array
    Client.GetData baData
    
    Debug.Print "Received " & bytesTotal & " bytes"
End Sub

Partial Reading

Private Sub m_oClient_DataArrival(Client As cWinsock, ByVal bytesTotal As Long)
    Dim sHeader As String
    Dim sBody As String
    
    ' Read first 10 bytes as header
    Client.GetData sHeader, vbString, 10
    Debug.Print "Header: " & sHeader
    
    ' Read remaining data
    Client.GetData sBody
    Debug.Print "Body: " & sBody
End Sub

Specified Encoding Reading

Private Sub m_oClient_DataArrival(Client As cWinsock, ByVal bytesTotal As Long)
    Dim sData As String
    
    ' Read using UTF-8 encoding
    Client.GetData sData, vbString, -1, ScpUtf8
    
    Debug.Print "UTF-8 data: " & sData
End Sub

Protocol Parsing

Private Type tPacketHeader
    Magic As Long ' Magic number
    Length As Long ' Data length
    Type As Long ' Data type
End Type

Private Sub m_oServer_DataArrival(Client As cWinsock, ByVal bytesTotal As Long)
    Dim tHeader As tPacketHeader
    Dim baBody() As Byte
    
    ' Read header
    Client.GetData tHeader
    
    ' Verify magic number
    If tHeader.Magic = &H12345678 Then
        ' Read data body
        ReDim baBody(0 To tHeader.Length - 1) As Byte
        Client.GetData baBody
        
        Debug.Print "Data type: " & tHeader.Type
        Debug.Print "Data length: " & tHeader.Length
    End If
End Sub

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👁️ PeekData Method

Description

Peek at data without removing from buffer.

Syntax

Public Sub PeekData(Data As Variant, Optional ByVal VarType_ As Long, Optional ByVal MaxLen As Long = -1, Optional ByVal CodePage As EnumScpCodePage = ScpAcp)

Parameters

Same as GetData.

Usage Example

Private Sub m_oClient_DataArrival(Client As cWinsock, ByVal bytesTotal As Long)
    Dim sPeek As String
    Dim sActual As String
    
    ' Peek at data first
    Client.PeekData sPeek
    Debug.Print "Peek data: " & sPeek
    
    ' Then read data
    Client.GetData sActual
    Debug.Print "Actual data: " & sActual
End Sub

Protocol Detection

Private Sub m_oServer_DataArrival(Client As cWinsock, ByVal bytesTotal As Long)
    Dim sPeek As String
    
    ' Peek at first few characters to detect protocol
    Client.PeekData sPeek, vbString, 4
    
    If Left$(sPeek, 4) = "HTTP" Then
        Debug.Print "HTTP request"
        HandleHttpRequest Client
    ElseIf Left$(sPeek, 4) = "CHAT" Then
        Debug.Print "Chat protocol"
        HandleChatMessage Client
    Else
        Debug.Print "Unknown protocol"
    End If
End Sub

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🔒 Close_ Method

Description

Close connection or stop listening.

Syntax

Public Sub Close_()

Usage Example

' Close client connection
Private Sub cmdDisconnect_Click()
    m_oClient.Close_
    Debug.Print "Disconnected"
End Sub

' Stop server
Private Sub cmdStopServer_Click()
    m_oServer.Close_
    Debug.Print "Server stopped"
End Sub

' Close specific client
Private Sub DisconnectClient(ByVal oClient As cWinsock)
    oClient.Close_
    m_oServer.RemoveClient oClient
End Sub

Auto Close

' Auto close when form unloads
Private Sub Form_Unload(Cancel As Integer)
    On Error Resume Next
    m_oClient.Close_
    m_oServer.Close_
    m_oUdp.Close_
End Sub

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📝 GetErrorDescription Method

Description

Get description of error code.

Syntax

Public Function GetErrorDescription(ByVal ErrorCode As Long) As String

Usage Example

Private Sub m_oClient_Error(Client As cWinsock, ByVal Number As Long, Description As String, ByVal Scode As Long)
    ' Use description from parameter
    Debug.Print "Error: " & Description
    
    ' Or use GetErrorDescription to get
    Debug.Print "Error description: " & Client.GetErrorDescription(Number)
End Sub

' Independent use
Dim sDesc As String
sDesc = m_oClient.GetErrorDescription(10060)
Debug.Print sDesc ' "Connection timeout"

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🤝 Friend Methods

The following methods are for internal use, usually don't need to call directly:

AcceptFrom

Accept new connection (called by OnAccept event).

SetUdpClientInfo

Set UDP virtual client info (called by OnReceive event).

RemoveClient

Remove client (called by CloseEvent or manually).

RaiseDataArrivalEvent

Trigger data arrival event (called by client object, triggered through parent server).

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📌 Method Usage Scenarios Summary

TCP Client Flow

1. m_oClient.Connect("127.0.0.1", 8080)
2. Wait for m_oClient_Connect event
3. m_oClient.SendData("Hello")
4. Wait for m_oClient_DataArrival event
5. Client.GetData sData
6. m_oClient.Close_()

TCP Server Flow

1. m_oServer.Listen(8080)
2. Wait for m_oServer_ConnectionRequest event
3. Set DisConnect = False to accept
4. Wait for m_oServer_DataArrival event
5. Client.GetData sData
6. Client.SendData("Reply")
7. Wait for m_oServer_CloseEvent event

UDP Flow

1. m_oUdp.Bind(8888)
2. Wait for m_oUdp_DataArrival event
3. Client.GetData sData
4. Client.SendData("Reply")
5. m_oUdp.Close_()

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Last Updated: 2026-01-09