How To Create a NetDDE Client and Server in Visual Basic

MORE INFORMATION

In order to establish a link to a remote application, a DDE share must be created on the remote computer. A DDE share consists of a Share Name, Application name, and a Topic. Shares may be created and edited using the DDE Share Manager (DDESHARE.EXE), which may be found in the <WINNT\SYSTEM32> directory on NT 4.0. For Windows 95, Windows 98, Windows Me, and Windows For Workgroups, the Network DDE Share Manager can be found in the Windows for Workgroups Resource Kit.

Creating the Visual Basic NetDDE Server

1. Start Visual Basic and create a new Standard EXE application. Form1 is created by default.
2. Place a Textbox (Text1) on Form1 and set the Text Property to "The DDE Server is Running."
3. Change the LinkMode Property of Form1 to "1 - Source."
4. Select Project1 Properties from the Project menu, select the Make tab, and then change the application title to DDESRV.
5. Compile and save the application and name it DDESRV.EXE.
6. Install the application on a computer on your network that you want to use as the Server.

Creating the DDE Share on the Server

1. Start the DDE Share Manager Application on the Computer designated as the Server. Select Run from the Windows Start menu, and then run DDESHARE.
2. Select "DDE Shares" from the "Shares" menu. A list of shares that have previously been set up will be displayed in the list box.
3. Click the "Add a Share" button.
4. Enter "DDETEST$" in the "Share Name" textbox.
   
   NOTE: When creating the share name it is not necessary to place a trailing "$," although it is conventional to do so.
5. Enter the following values in the corresponding Application and Topic Text boxes:

                         Application Name              Topic Name
                        -------------------          ---------------
      oldstyle             DDESRV.DDE                    Form1
      newsytle             DDESRV.OLE                    Form1
      static               DDESRV                        Form1
   
   						

   NOTE: The DDESHARE utility for WFW/WIN95/WIN98 only supports defining one Application and Topic name each. Use the static Application and Topic names from the list above.
6. Click OK to close the DDE Share Properties dialog.
   
   IMPORTANT: Due to a bug in the DDE Share Utility, when exiting the DDE Share application, a new serial number is created for the Share but is not updated in the Trusted DDE Shares section of the registry; therefore, the next two steps are very important.
7. Select the DDETEST$ share in the list and click on the "Trust Share" button.
8. Make sure that "Initiate to Application Enable" is selected and then click the "SET" button.
9. Press OK on both open dialogs and then exit the DDE Share Utility.

Creating and Testing the Visual Basic NetDDE Client

1. Start a new Standard EXE project in Visual Basic. Form1 is created by default.
2. Add a CommandButton to Form1. Change the following properties:

      Name:     cmdConnect
      Caption:  Connect
   
   					

3. Add a Text box to Form1 and name it txtData.
4. Paste the following code into the Declarations Section of Form1:
   
   NOTE: Replace the <MACHINE NAME> with the appropriate computer name where the DDE SRV application will be running.

         Private Sub cmdConnect_Click()
            txtData.linkMode = vbLinkNone
            txtData.linkTopic = "\\<MACHINE NAME>\NDDE$|DDETEST$
            txtData.LinkItem = "Text1"
            txtData.LinkMode = vbLinkManual
            txtData.LinkRequest
         End Sub
   
   					

5. Start the DDESRV application on the Network computer acting as the DDE Server.
6. Press the F5 key to run this client within the Visual Basic 5.0 IDE.
7. Click the Command button labeled "Connect" and note that the string "The DDE Server is Running" appears within the txtData Text Box.