Troubleshooting SQL Azure Connectivity

How to resolve some of the common connectivity error messages that you would see while connecting to SQL Azure

• A transport-level error has occurred when receiving results from the server. (Provider: TCP Provider, error: 0 - An existing connection was forcibly closed by the remote host.)
• System.Data.SqlClient.SqlException: Timeout expired.  The timeout period elapsed prior to completion of the operation or the server is not responding. The statement has been terminated.
• An error has occurred while establishing a connection to the server. When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections
• Error: Microsoft SQL Native Client: Unable to complete login process due to delay in opening server connection.
• A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

Some troubleshooting tips

a) Verify Azure Firewall Settings and Service Availability
    Reference: SQL Azure Firewall - http://msdn.microsoft.com/en-us/library/ee621782.aspx

b) Verify that you can reach our Virtual IP
    Reference: Telnet Troubleshooting Guide - http://technet.microsoft.com/en-us/library/cc753360(WS.10).aspx

   Reference: How to Use TRACERT to Troubleshoot TCP/IP Problems in Windows - http://support.microsoft.com/kb/314868

c) Windows Firewall on the local machine
    Frequently Asked Questions - http://msdn.microsoft.com/en-us/library/bb736261(VS.85).aspx

    Reference: Windows Firewall with Advanced Security Getting Started Guide - http://technet.microsoft.com/en-us/library/cc748991(WS.10).aspx

d) Other Firewall products

    Reference: http://www.whatismyip.com/

e) Generate a Network Trace using Microsoft Network Monitor tool

   Reference: How to capture network traffic with Network Monitor - http://support.microsoft.com/kb/148942

f) SQL Azure Denial of Service (DOS) Guard

SQL Azure utilizes techniques to prevent denial of service attacks. If your connection is getting reset by our service due to a potential DOS attack you would  be able to see a three way handshake established and then a RESET in your network trace.