One other related service that deserves special attention is
the SQL Server Browser service. This service is particularly important if you
have named instances of SQL Server running on a machine. SQL Server Browser
listens for requests to access SQL Server resources and provides information
about the various SQL Server instances installed on the computer where the
Browser service is running.
Prior to SQL
Server 2000, only one installation of SQL Server could be on a machine at one
time, and there really was no concept of an “instance.” SQL Server always
listened for incoming requests on port 1433, but any port can be used by only
one connection at a time. When SQL Server 2000 introduced support for multiple
instances of SQL Server, a new protocol
called SQL Server Resolution Protocol (SSRP) was developed to listen on UDP port 1434. This listener
could reply to clients with the names of installed SQL Server instances, along
with the port numbers or named pipes used by the instance. SQL Server 2005
replaced SSRP with the SQL Server Browser service, which is still used in SQL
Server 2008.
If the SQL Server
Browser service is not running on a computer, you cannot connect to SQL Server
on that machine unless you provide the correct port number. However, if the SQL
Server Browser service is not running, the following connections will not work:
- Connecting to a named instance without providing the port number or pipe
- Using the DAC to connect to a named instance or the default instance if it us not using TCP/IP port 1433
- Enumerating servers in Management Studio, Enterprise Manager, or Query Analyzer
It is
recommended that the Browser Service be set to start automatically on any
machine onwhich
SQL Server will be accessed using a network connection.
