I am writing a custom server for a client. They want scalability so I must use a thread pool and probably I/O completion port to regulate it. The main requirement is that a windows service manage the HTTP requests for a number of reasons.

An example of one would be that a client session spans many requests and continuity must be maintained. Another would be that the ISAPI Dll will be in the IIS address space and so it's code will be lean and very carefully implemented. The extensive processing in the Windows service may get unruly for the duration of the lengthy development. If the service crashes it will not take out IIS.

Anyway, the remaining decision is how to have these two processes communicate. We have talked about pipes, tcp, global memory and even a single pipe with multiplexed data ala FastCGI.

Would love to hear anyones experience with a decision like this.