General Networking Error and Firewalls

 

If you receive a “general network error”, and there is no obvious reason for the error, then you might want to take a look at your firewall settings.

 

We had a case recently where one of our most important customers was seeing on rare occasions a transaction failure on a SaveChanges call to the Persistence Manager.   We noticed that a "Network error" accompanied the failure, but we could never understand the details.  Eventually, we included better diagnostics, and then discovered that the network failure was due to the fact that the provider was sending null packets to the SQL Server.  These null packets conformed to the pattern of a Denial of Service (DOS) attack, and the firewall then terminated the communication.  In fact, this was a false positive.  The null  packets were harmless.  The fix was to modify the firewall settings: