#127 Support for hostnames with multiple addresses

[Christoph Hohmann]

To support SQL Server 2013 with high availability it is required, that all possible IP addresses of a SQL server hostname are tried when establishing a connection to a server.

The high availability feature of SQL Server 2013 using availability groups creates one or multiple virtual IP addresses for a HA cluster and then creates a hostname in the DNS server that returns all virtual IP addresses. If there are multiple addresses (for example if servers are located in multiple subnets) the driver currently only tries the first address. If this is the address of a server, that is currently not accepting connection, the connection will fail, even if a connection to one of the other IP addresses would work.

This patch adds support for multiple IP addresses to the SharedSocket. When a connection to a host is opened, all addresses will be tried until the first connection is successfully established. Otherwise if all addresses fail, the connection will fail like before. It is only implemented for the JDBC3 connection code.