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I have an old app that is a DDE server. I access if with my app that connects and gets data points. All has been working until Windows 10. Now the server app does not respond to the data requests. This is not using NetDDE. All communications are between apps on the same computer, started by the same user.

Does anyone have an explanation for this problem. Is there some new security protocol that must be implemented? I have searched extensively, but most posts on the subject are with regard to Microsoft Office programs, and networking issues with DDE.

Thanks, Russ

What I have tried:

Using Spy++ to see that there are no responses to the DDE request.
Updated 9-Aug-21 6:50am
Dave Kreskowiak 9-Aug-21 13:26pm    
Not a solution, but DDE is so ridden with security issues, it shouldn't be used by anything.

Microsoft has finally put options into Office to disable DDE between Office apps after a decade of people screaming about it.
Russ Pillsbury 9-Aug-21 15:02pm    
Well, ok, but I have no choice because I did not write the server app, have no source, and no support. And no other app that can do what this one does. Also, how is it a security risk when both apps are running on the same machine. As long as the machines themselves are secure I do not see how DDE is a risk at all.

In any case I really would like to have some idea if this is fixable by some permission setting or perhaps modification to the DDE client (which IS my program).
Dave Kreskowiak 9-Aug-21 15:14pm    
DDE has been full of security holes since it's inception, decades ago. It may not be obvious to you, but think about it this way. How does the DDE server app know which app is calling it and running under which account?

Hint: It doesn't.
Russ Pillsbury 9-Aug-21 15:53pm    
Right, but that doesn't matter because the user of the computer controls both apps. There is no case where an outside connection can make it different than what the user sets up. These apps are designed to run in a stand-alone situation, often without even internet access. The server reports the position of a satellite, and the client positions an antenna to track it. How can that not be secure?
Dave Kreskowiak 9-Aug-21 16:02pm    
I'm not saying this stuff applies to you directly. I'm saying this is why DDE is a dead technology.

If you have the capability of rewriting the server app, and use a different IPC method, do it.

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