KB152058 - HOWTO: Send and Receive UDT's Using the Winsock Control

Article ID: 152058

Article Last Modified on 3/18/2005

Microsoft Visual Basic 4.0 Standard Edition
Microsoft Visual Basic 4.0 Professional Edition
Microsoft Visual Basic 4.0 32-Bit Enterprise Edition
Microsoft Internet ActiveX Controls 1.0

This article was previously published under Q152058

SUMMARY

The Winsock control methods SendData and GetData send and receive data through an argument declared of type variant. The following variant types are supported:

   Byte        vbByte
   Integer     vbInteger
   Long        vbLong
   Single      vbSingle
   Double      vbDouble
   Currency    vbCurrency
   Date        vbDate
   Boolean     vbBoolean
   SCODE       vbError
   String      vbString
   Byte Array  vbArray + vbByte

Because user-defined types are not directly supported, you must make use of the byte-array data type in order to pass a user-defined type with the Winsock control. This article demonstrates how to send and receive data contained in a user-defined type with the Winsock Control.

MORE INFORMATION

The example uses the Winsock TCP client and server created in the following Microsoft Knowledge Base article:

152057 HOWTO: Create & Use a Client/Server Using Winsock TCP Controls

Prior to following this example, make sure you have at least built the framework for the client and server discussed in the aforementioned article. You will be required to make modifications to the DataArrival Event subroutine and the SendData Command subroutine.

Step by Step Example

Enter the following code in the General declarations section of Form1 of both the client and server:

   Private Declare Sub CopyMemory Lib "KERNEL32" Alias "RtlMoveMemory" (_
          hpvDest As Any, hpvSource As Any, ByVal cbCopy As Long)

   Private Type MyType
      i As Integer
      l As Long
      s As String * 8
      d As Double
   End Type

Enter the following code for the DataArrival Event subroutine in the Winsock server:

   Private Sub TCP1_DataArrival(Index As Integer, ByVal bytesTotal As Long)
         Dim vta
         Dim mt As MyType
         Dim bt() As Byte
         TCP1(Index).GetData vta, vbArray + vbByte, LenB(mt)
         bt = vta
         CopyMemory mt, bt(0),  LenB(mt)
         Debug.Print mt.i; ","; mt.l; ","; mt.s; ","; mt.d
      End Sub

Enter the following code for the SendData Command button in the Winsock client:

   Private Sub cmdSendData_Click()
         Dim mt As MyType
         mt.i = 99
         mt.l = 33
         mt.s = "abcd"
         mt.d = 23.76
         Dim bt() As Byte
         ReDim bt(LenB(mt)) as Byte
         Dim vtdata As Variant
         CopyMemory bt(0), mt, LenB(mt)
         vtdata = bt
         TCP1.SendData vtdata
      End Sub

Keywords: kbwinsock kbapi kbnetwork KB152058