Microsoft® SQL Server™ uses a dynamic-link library (DLL) called a Net-Library to communicate with a particular network protocol. A matching pair of Net-Libraries must be active on client and server computers to support the desired network protocol (all of the SQL Server client and server Net-Libraries are installed during SQL Server Setup). For example, to enable a client application to communicate with a specific SQL Server across TCP/IP, the client TCP/IP Sockets Net-Library (Dbmssocn.dll) must be configured to connect to that server on the client computer, and the server TCP/IP Sockets Net-Library (Ssmsso70.dll) must be listening on the server computer.
By themselves, a pair of Net-Libraries cannot support a client/server connection. Both the client and server must also be running a protocol stack supporting the Net-Libraries. For example, if the server TCP/IP Sockets Net-Library is listening on the server computer, and the client TCP/IP Sockets Net-Library is configured to connect to that server on the client computer, the client can only connect to the server if a TCP/IP protocol stack is installed on both computers.
The Named Pipes and Multiprotocol Net-Libraries both support multiple network protocols (NW Link IPX/SPX, NetBEUI, and TCP/IP), and will automatically select any supported network protocol that is available. Using either of these Net-Libraries is useful if the client must connect to multiple servers running different network protocols, and you do not want to create and manage configuration entries for each server-network protocol combination.
The client Net-Libraries are installed during SQL Server Setup. You define which client Net-Libraries are used to connect to particular servers using the SQL Server Client Network Utility. You can specify a default Net-Library for all connections, and also define the use of specific Net-Libraries for connecting to specific servers. Named Pipes is the default Net-Library on clients running Microsoft Windows NT® or Microsoft Windows® 95/98.
SQL Server on a server running Windows 95/98 does not support the server Named Pipes Net-Library. In that case, either the default Net-Library for the client must be changed to TCP/IP Sockets or Multiprotocol, or a new configuration entry must be created on clients using one of those Net-Libraries.
SQL Server can be listening simultaneously on any combination of server Net-Libraries. During SQL Server Setup, or after setup, using SQL Server Network Library Configuration, you can choose the server Net-Libraries to be activated. The default server Net-Libraries on which SQL Server listens are:
For computers running Windows NT
For computers running Windows 95/98
For more information about the SQL Server Net-Libraries and the network protocols they support, see Communication Components.