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

• Microsoft Visual Basic Standard, Professional, and Enterprise Editions, 32-bit only, for Windows, version 4.0
• Microsoft ActiveX Internet Controls version 1.0

SUMMARY

The Internet Control Pack contains the Winsock control that allows you to connect to a remote machine and exchange data dynamically between computers in both directions. This article demonstrates the steps required to create a minimal client and server relationship for exchanging data between computers. The Winsock TCP control, a connection-based control, is used to create the client and server.

MORE INFORMATION

Phase One - Create the Server

1. Start a new project in Visual Basic. Form1 is created by default.



2. From the Tools menu, choose Custom Controls, and add a reference to Microsoft Winsock Controls.



3. Add a Winsock TCP control to the Form, and change the control's index property to zero.



4. Add the following code to the general declarations section of Form1:
   

   
         Private gSockInstance
   
         Private Sub Form_Load()
            gSockInstance = 0
            TCP1(0).LocalPort = 1007
            TCP1(0).Listen
         End Sub
   
         Private Sub TCP1_ConnectionRequest(Index As Integer, _
                                            ByVal requestID As Long)
            gSockInstance = gSockInstance + 1
            Load TCP1(gSockInstance)
            TCP1(gSockInstance).Accept requestID
         End Sub
   
         Private Sub TCP1_DataArrival(Index As Integer, ByVal bytesTotal _
                                      As Long)
            Dim vta
            TCP1(Index).GetData vta, vbString
            MsgBox vta, 0, "Server"
         End Sub 




5. Choose Start from the Run menu, or press the F5 key to start the program.



6. Minimize Visual Basic.

Phase Two - Create a Client

1. Start a second copy of Visual Basic. A new project (Project1) with a default form (Form1) is created.



2. From the Tools menu, choose Custom Controls, and add a reference to Microsoft Winsock Controls.



3. Add a Winsock TCP control and two Command buttons to the Form. Change the Captions of the Command buttons to "Connect" and "SendData".



4. Add the following code to the Connect button Click event:
   

   
         Private Sub Command1_Click()
            With TCP1
              .RemoteHost = "machine name you specify"
              .RemotePort = 1007
              .Connect
            End With
         End Sub 




5. Add the following code to the SendData button Click event:
   

   
         Private Sub Command2_Click()
            TCP1.SendData "This is how we begin"
         End Sub 




6. Add the following code to the TCP1_Connect event:
   

   
         Private Sub TCP1_Connect()
            If (TCP1.State = sckConnected) Then
               MsgBox "connection successful"
            Else
               MsgBox "connection failed"
            End If
         End Sub 

   
   For demonstration purposes of this article, the client and server execute on the same machine. TCP1.RemoteHost is specified as the machine where the server is running. However, a simple change to the RemoteHost property will allow you to connect to any machine with a Point-to-Point connection.



7. Choosing Start from the Run menu, or press the F5 key to start the program.



8. Press the Connect button, and the message box is displayed stating that the connection was successful.



9. Press the SendData button, and a message box containing the data that was sent is displayed from the server.

Keywords          : kbnetwork kbAPI kbSDKPlatform kbVBp400 kbWinsock kbGrpNet 
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Last Reviewed: March 10, 1999