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Kepware Knowledge Base: Solution


Unable to Connect with a NetDDE Client


Last Update: 11/7/2018

NetDDE enables communication between DDE applications installed on remote computers. Due to security concerns, NetDDE was disabled starting with Windows Server 2003 and Windows XP SP2. It was later completely removed from Windows Vista and newer operating systems.

When using NetDDE on a supported operating system, ensure that the NetDDE service is started on both the client and server computer. It will also be necessary to allow UDP Port 137 and TCP Ports 135 and 139 through the firewall.