Web server open error: "HTTP could not register URL"

Web server open error: "HTTP could not register URL"

The TopView Application log may show the following error message: 
Web server open error: HTTP could not register URL http://+:7170/. Your process does not have access rights to this namespace.

Background

The TopView Mobile Web App communicates to TopView's embedded Web Server, which is built upon Windows HTTP Server API (AKA Http.Sys). When the user enables the Mobile Web App, they select the listen port for the web server (7170 in the above sample error message). When the TopView Engine starts, it opens a listener on the configured web server port. If the user account of the TopView Engine (i.e. the logged in user if run interactively, or the Service LogOn account if run as a service) does not have permission to open the listen port for the web server, the above error occurs.

Fix

On Vista and later operating systems (Windows 7, Windows Server 2008, ...), follow these steps:
  1. Launch a command prompt as Administrator or elevated privilege
  2. Enter the following command: 
    netsh http add urlacl url=http://+:{port number}/ user={user account name}
    ...replacing {port number} with the web server port, and {user account name} with the user. Example: 
    netsh http add urlacl url=http://+:7170/ user=DOMAIN\user

Resources and more information

The command for registering a port for a user account is described in Microsoft's Preregister URL prefixes and configure SSL section of its Http.Sys article. For earlier operating systems and for more details about this issue, see the similar section on Configuring Namespace Reservations in Microsoft's Configuring HTTP and HTTPS article.