BranchCache service blocking port 80

Windows Server gotcha

Just spent an extremely aggravating three hours tracking down a problem on Windows Server where a Webmail service simply would not work. I suspected that something was grabbing ports 80 and/or 443.. and in principle I was right. The issue lay in finding our exactly what was hogging the port.

Sysinternals TCPView showed that port 80 was indeed being hijacked, but by a process cryptically described as 'System' and a PID of 4.

A search suggested that IIS might be responsible.

The computer has IIS installed on it but not running. I would rather have kept IIS intact for possible later use on a different  port, but in view of the cryptic nature of the problem  there seemed to be no alternative to some 'hack and slash' diagnostics. So, with a good backup under my belt,  Server Manager was opened, and all IIS components consigned to the trashcan.

On restart, I was perplexed to see no change in the situation.

The possibility of malware or a rootkit did cross my mind, but as this was a recent install that seemed unlikely.

So, opening services.msc I decided to just go through all the services that might possibly be causing the problem, stopping them.

Having tried all the likely candidates with no joy, I then just resorted to turning off all services starting at A. I was well aware that the computer might start to misbehave or reboot at some point, but what the heck, the problem had to be found, and this was the last resort short of a complete reinstall. 

I'd got to the B's when I just happened to notice a change in the TCPView window, visible in the background. Yes, port 80 was -at long last- clear.  It was then just a process of elimination to determine that BranchCache was the culprit.

Now that I knew what search keywords to use, I found references to others having this problem. Although, it doesn't seem to be a well-known issue. 

I really have to wonder what the developers were thinking when they included a service whose presence stops Web services on the standard ports from working properly, which is ON by default, and which even when advanced diagnostic tools are brought to bear on the problem, is nigh-impossible to identify as the culprit.

Think this underlines the problems involved in upgrading Windows systems, in that the latest versions contain way too many unwanted gimmicks. These gimmicks aren't just dead weight either, they can seriously ruin your day  when they prevent the functions you do need from working properly.


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