或者参考 http://msdn2.microsoft.com/en-us/library/ms181087.aspx
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Background
Prior to Microsoft SQL Server 2000, only one instance of SQL Server could be installed on a computer. SQL Server listened for incoming requests on port 1433, assigned to SQL Server by the official Internet Assigned Numbers Authority (IANA). Only one instance of SQL Server can use a port, so when SQL Server 2000 introduced support for multiple instances of SQL Server, SQL Server Resolution Protocol (SSRP) was developed to listen on UDP port 1434. This listener service responded to client requests with the names of the installed instances, and the ports or named pipes used by the instance. To resolve limitations of the SSRP system, SQL Server 2005 introduces the SQL Server Browser service as a replacement for SSRP.
How SQL Server Browser Works
When an instance of SQL Server starts, if the TCP/IP or VIA protocols are enabled for SQL Server, the server is assigned a TCP/IP port. If the named pipes protocol is enabled, SQL Server listens on a specific named pipe. This port, or "pipe," is used by that specific instance to exchange data with client applications. During installation, TCP port 1433 and pipe \sql\query are assigned to the default instance, but those can be changed later by the server administrator using SQL Server Configuration Manager. Because only one instance of SQL Server can use a port or pipe, different port numbers and pipe names are assigned for named instances, including SQL Server Express. By default, when enabled, both named instances and SQL Server Express are configured to use dynamic ports, that is, an available port is assigned when SQL Server starts. If you want, a specific port can be assigned to an instance of SQL Server. When connecting, clients can specify a specific port; but if the port is dynamically assigned, the port number can change anytime SQL Server is restarted, so the correct port number is unknown to the client.
Upon startup, SQL Server Browser starts and claims UDP port 1434. SQL Server Browser reads the registry, identifies all instances of SQL Server on the computer, and notes the ports and named pipes that they use. When a server has two or more network cards, SQL Server Browser returns the first enabled port it encounters for SQL Server. SQL Server 2005 and SQL Server Browser support ipv6 and ipv4.
When SQL Server 2000 and SQL Server 2005 clients request SQL Server resources on a named instance, the client network library sends a UDP message to the server using port 1434. SQL Server Browser responds with the TCP/IP port or named pipe of the requested instance. The network library on the client application then completes the connection by sending a request to the server using the port or named pipe of the desired instance.
For information about starting and stopping the SQL Server Browser service, see "How to: Start and Stop the SQL Server Browser Service" in SQL Server Books Online. |
发表于 2008-3-27 16:53:11
