I have written a web server application using ASP.Net that handles requests from an HTTP client. I wrote a small test client in VB6 using the MSINet ActiveX control, to load test the server. The client makes repeated requests of the server and keeps track of the number per second it is able to get processed. When I run both the client and server on one machine, I get about 150 per second. When I move the client to another machine on my LAN, the number drops to 3. Each request is only about 100 bytes, so there is no bandwidth issue. Both CPUs are showing near zero usage. I get the same result from 2 different client machines. I even tried a different ActiveX control, a commercial one, but the same thing happens. Where could the bottleneck be? The client makes a request, waits for the response, and then makes another request. The server is a plain vanilla .net web application, nothing fancy. I am completely stumped.
Followup:
After further experimentation I have discovered the following. If I simplify the page to just a tiny .html file, the performance jumps considerably. If I take the same file and change the extension to .aspx, performance tanks. If I change it to .asp, it performs slightly worse than the .html version. The file contains one line of html, so there is no processing to be done by the server. It would seem that there is something bad happening in aspnet_isapi.dll when the client is on a different machine.
Followup:
This is getting even more bizarre. I decided to cut out all the middlemen and code directly to the winsock dll. The problem disappeared! Then, I downloaded a commercial Winsock ActiveX control and rolled my own HTTP. Surprise, surprise, the problem returned. I have tried 4 different HTTP/Winsock ActiveX packages, on a number of different clients and servers, using two different programming languages, on 2 different LANs, and all show exactly the same behavior. What the heck is going on here?!?!
