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

Originally published on December 17, 2008 by Sascha Neumeier
Last updated on December 06, 2022 • 8 minute read

Hello, nice to have you here.

You've found a real oldie but goodie here on our blog. 🕺🏼
The original content is from 2008, and a lot has happened since then.

Our free Webserver Stress Tool is not supported anymore. Of course you can still download and use it.

It's also pretty sure that you won't get the error mentioned in the headline in our Webserver Stress Tool - but maybe in another software or script. And probably that's why you are here, because of a general problem around Windows Error 10049.


So that your click was not wasted, and we can still help you, just continue reading for a few more seconds...

The error “Cannot assign requested address” suggests that the hostname/IP you are trying to bind does not resolve to a local network interface.

There are several causes for this error, depending on which application or service you are using. Generally, the problems occur because of the TCP/IP cache and stack.

For example, the problem may be related to improperly configured proxy settings. If you encounter this error while working with Python, then the problem may be with ftplib because it is unable to connect to the target device.

There is an extensive explanation at technipost.com about what you can do about this error: Guide to Fix The Requested Address is Not Valid in its Context Error Problem

And don't forget! If you're looking for a really neat monitoring solution, whether for your network, IT or IIoT environment, check out Paessler PRTG! ❤️

Paessler PRTG and is available in different editions:

Have a great time! 🙃

Recently some users of our product  found out that they could not perform any load tests anymore - but it had worked fine on their Vista computers before.

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.

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