Starting network DDE services

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Starting network DDE services

For Network DDE to function, NetDDE.EXE needs to be installed and running on both machines before attempting to conduct a Network DDE conversation. NetDDE.exe is a Windows Service system file that is used to communicate the shared dynamic data exchange used by Network DDE. It has no graphical user interface (it runs as a background Windows service).

It is necessary to initiate the automatic activation of Network DDE Services, or manually run NetDDE.EXE on both machines before attempting connection.

To manually start Network DDE services:

On the Windows Start menu, click Start | Run, type in "netdde" (without the quotes) and press the Enter key. Do so on both machines.

To automatically start the Network DDE Services on machine startup:

With Windows 2000 and later, use the Windows Services Manager (select Start | Control Panel | Administrative Tools | Services) to set the Network DDE servicefrom Manual to Automatic. To do so, right-click the service and select Properties from the pop-up menu. On the General tab select Automatic from the drop-down list of the Startup type field. Click OK. Close evry window and restart the machine.

To verify that the NetDDE Services are running:

The Windows Task Manager lists NetDDE.exe on the Processes tab when running. To view the Windows Task Manager, press CTRL+ALT+DEL.
The Service Administrative Tools also lists the status of Network DDE and Network DDE DSDM. To view the Windows Services Manager, select Start | Settings | Control Panel | Administrative Tools | Services.
Note: If you are using only the Microsoft Client Service for NetWare Networks, the NW IPX/SPX/NetBIOS compatible protocol needs to be enabled for NetDDE.exe to load.

To test that Network DDE is operational between two machines on the same network

Microsoft Windows ships with a network DDE application called Chat. It is installed in the system32 folder.

On the Windows Start menu, click Start | Run, type in "winchat" (without the quotes) and press the Enter key. Do so on both machines.
On one machine, select the Chat menu Conversation | Dial or click the dial button. The Select Computer dialog will display.
Select the other computer from the list, and click OK. Chat will attempt to establish a network DDE conversation between the computers.
Note: If Chat is not already running on the other computer, it times-out and states that the other computer didn't answer. If however, the other computer is already running Chat, it will keep dialling until answered.
On the other machine, (while it is being dialed), select the Chat menu Conversation | Answer or click the answer button. Type in a message and it will display in the Chat window on the other machine. The conversation will continue until either machine hangs up.

Once a Chat conversation is established, it proves that both machines are properly set-up and capable of handling network DDE conversations. You can view the share properties for Chat$ by using the DDEShares.exe application as described in Setting up network DDE shares.

You don't have to run Chat to use Network DDE with CitectSCADA. This Network DDE test only uses Chat as an example to confirm Network DDE functionality between two machines. Once you have established that Network DDE is functional, close the Chat windows, create the Network DDE Trusted Share for your Network DDE server application, and connect to the share using Network DDE. See Connecting to a network DDE shared application.