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Dynamic Data Exchange (DDE) is a Microsoft protocol for exchanging data between Windows applications. It establishes communication channels between client and server applications, and can be executed once or dynamically updated. DDE has been superseded by OLE and COM, but is still used for certain purposes.
Dynamic Date Exchange (DDE) is a Microsoft® message-based computer protocol that allows data to be exchanged between applications running on Windows operating systems. Known more generally as inter-process communication, Dynamic Data Exchange transmits messages to establish a “talk” and communication channel between the application requesting the data, the client, and the application where the data resides, ie the server. Written and initiated by the client application, a DDE request consists of the name of the server’s DDE application, the nature of the data to be exchanged, called the DDE argument, and the name of the DDE element. DDE connections can be executed once or dynamically updated, in which case the receiving application is notified whenever the value of the specified data on the server application changes. Multiple DDE connections can be established from any application, and an application can act as a client and server simultaneously.
Dynamic Data Exchange works by broadcasting messages containing the DDE request to all other running applications. If a running application acknowledges the DDE request, it responds and a conversation is established. The Windows operating system then establishes a link between the two applications. Communication channels can be one-time or permanent in cases where the client application needs to have updated data on a regular basis. There are two types of permanent links: warm and hot. Hot links require user approval first to update the client application. With hot links this is done automatically.
DDE data communication happens behind the scenes, meaning the user can continue doing what they are doing while the DDE request runs in the background. Therefore, Dynamic Data Exchange communication is referred to as asynchronous. The DDE request and its result can be stored in shared memory while the client and server applications continue their ongoing processing until the request and response can be performed.
This protocol has to some extent been superseded by Microsoft® Object Linking and Embedding (OLE) and Component Object Model (COM), as well as the Dynamic Data Exchange Management Library (DDEML). However, DDE is still widely used for certain purposes, especially those that don’t require continuous user interaction. Examples include updating a Microsoft® Excel spreadsheet client from server applications that receive real-time data from sensors or other measurement devices on a production line, connecting to applications that receive real-time actions, and other updates on the financial markets or regularly updating a value sheet from a database.
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