DLL Surrogates

COM now makes it possible to create DLL servers that can be loaded into a surrogate EXE process. This combines the ease of writing DLL servers with the benefits of executable implementation. Standard development tools like Microsoft® Visual Basic®, Microsoft® Visual J++™, and Microsoft® Visual Studio™ facilitate the writing of DLL servers, but a DLL server in itself has limits. Running the DLL server in a surrogate process offers several possible benefits:

• Fault isolation and the ability to service multiple clients simultaneously.
• In a distributed environment, a DLL server implementation could be used to service remote clients.
• It could permit clients to protect themselves from untrusted server code, while allowing them access to the services the DLL server provides.
• Running a DLL server in a surrogate provides the DLL with the surrogate's security.

COM provides a default surrogate process, or you can write a custom surrogate if you have special needs. These sections provide more information on DLL surrogates:

• DLL Server Requirements
• Registering the DLL Server for Surrogate Activation
• Using the System-Supplied Surrogate
• Writing a Custom Surrogate