"Cannot Assign Requested Address (#10049)" Errors in Webserver Stress Tool under Vista

What is the problem?

When a load test is run Webserver Stress Tool does not send out any HTTP requests, all requests end up in an error 10049 (Cannot Assign Requested Address). In the user0001.log the error messages look like this: 16.12.2008 11:25:31: User #1 Click #1: CLICK-Request 1: Time=2 ms, TFB=0 ms, Bytes=0, HTTP-StatusCode=404 (Not Found) Socketcode = 10049 (Cannot assign requested address.) Address not available (Error #10049) This error message says that the operating system does not allow Webstress to use a specific local IP address - even though the IP addresses that Webstress wants to use are only those that are configured on the system. All these customers were using Webstress on Vista computers.

When and why does this happen?

Our QA team ran a number of tests and found out:

• Windows 2000 and XP: Webstress works fine
• Windows XP: Webstress works fine
• Windows 2003: Webstress works fine
• Windows Vista SP1: Error 10049
• Windows Vista SP2: Error 10049
• Windows 2008: Webstress works fine
• Windows 2008 SP2: Webstress works fine

I must admit that we can not yet explain why this happens on Vista. Disabling virus software or Windows Firewall, reconfiguring the network settings, and some other reconfigurations did not change anything. We assume that a recent patch for Windows Vista, installed by Windows Update, changed something in the behaviour of Windows Vista which caused the problem.

Solutions

We have uploaded a new version of Webserver Stress Tool that offers an "automatic" option for the "Local IP" setting. On Vista you must currently use this option, you can not select the outgoing IP manually. Or you must use a computer for load testing which does not run under Windows Vista.