Background: Winsock LSPs and why they break ASP.NET

In 2007 it was very common for laptops to ship with mobile broadband software — UMTS / HSDPA dongles or built-in 3G modems came with bundled connection managers from Vodafone, T-Mobile, Sony Ericsson, and others. A lot of that software installed a Layered Service Provider (LSP) into the Windows Winsock chain so it could intercept and inspect TCP/IP traffic for connection management, traffic accounting, or “smart” routing between Wi-Fi and cellular.

The problem was that LSPs are notoriously fragile. A buggy or partially-uninstalled LSP can corrupt the Winsock catalog and break any application that goes through the socket layer — and ASP.NET / IIS, plus the Visual Studio web project tooling that talks to the local web server, are very much in that category. The classic symptom was exactly what I hit: Visual Studio hanging the moment it tried to create or open a web project, with the only previous “fix” being a full OS reinstall.

The post (originally)

I just found a solution to the issue in the subject. I had the problem a while ago and the only resolution was to re-install my machine. Today I had the same issue again after installing (what I figured out) an UMTS software on my machine. ASP.NET and IIS worked just fine before, but after installing the UMTS software this morning I had the same problems again. I googled and fortunately found this post. The resolution is just to run the little application attached. This will remove the bmnet.dll installed and will fix settings within the windows socket layer. It worked for me.

Looking back

The bmnet.dll referenced in the KB article was a specific LSP shipped by Bsquare with a number of vendor-bundled tools. The little Microsoft utility attached to KB910435 walked the Winsock catalog, identified the offending entry, and unhooked it cleanly without leaving the socket chain in a broken state.

If you ever hit the same family of symptoms today — sockets working partially, web tooling hanging, networking flaky after installing some piece of “helper” software — the modern equivalent is a one-liner from an elevated command prompt:

netsh winsock reset

Followed by a reboot. That command resets the Winsock catalog to its default state and removes any third-party LSPs that have been registered. It’s saved me more than once on machines where some VPN client, antivirus product, or older mobile broadband manager left things in an inconsistent state. Worth knowing about even if you never see this exact 2007 symptom again — the underlying mechanism is still in Windows.