A connection was successfully established with the server, but then an error occurred during the login process. (Microsoft SQL Server, Error 233)

Error: A connection was successfully established with the server, but then an error occurred during the login process. (provider: Shared Memory Provider, error: 0 - No process is on the other end of the pipe.) (.Net SqlClient Data Provider)

Solution:

Step 1: Open SQL Server Configuration Manager

• Go to Windows 8 Start screen.
• Start typing in SQLServerManager11.msc if you are looking for SQL Server 2012 configuration manager. Type in SQLServerManager10.msc if you are looking for SQL Server 2008 configuration manager.
• In the result panel you can see the SQLServerConfiguration Manager.
• Click the icon to launch the SQL Server Configuration manager.
• The configuration manager will open in MMC.

Step 2: Enable following configuration settings

1. ensure Shared Memory protocol is enabled
2. ensure Named Pipes protocol is enabled
3. ensure TCP/IP is enabled, and s ahead of the Named Pipes in the settings

Reference link: 
Stackoverflow
Could not open a connection to SQL Server