Clients cannot communicate to SQL Server through port 1433 or the port SQL Server is listening on

In some situations, clients may not be able to communicate to SQL Server through port 1433 or the port SQL Server is listening on. The following error may be seen in the error log:

SQL Server 2000: SQL Server 7.0:

Another application or service has taken control of the port before SQL Server starts. (Although port 1433 is reserved for use by SQL Server, Winsock applications use random ports above 1024 and therefore may bind to port 1433.)

This problem has additional potential causes. If the workaround in this article does not resolve the problem, see the following articles in the Microsoft Knowledge Base:

As mentioned in the "Network Libraries" topic in the refresh version of SQL Server 2000 Books Online, configuring SQL Server 2000 instances to use a dynamic port instead of a static port can reduce the chances of this problem occurring. However, with a dynamic port you have additional client connectivity and firewall issues to deal with. To determine what application is using the port, follow these steps:

• Stop all applications and third-party software services. Only the default services should be running on the server.
  
  Note A list of the services is in the "More Information" section.
• After the applications and services are stopped, start SQL Server. This will enable SQL Server to take control of port 1433.

If it is not possible to manually stop all third-party services every time that SQL Server is restarted, it would be better to create dependencies so that all the third-party services are dependent on the SQL service.

For additional information on resolving this problem, click the article number below to view the article in the Microsoft Knowledge Base:

Default Services

Default services for Microsoft Windows NT 4.0 and Microsoft Windows 2000 are provided below. In addition to these default services, other services may be listed in the Services dialog box for a computer (for example, network transports or other services that have been installed on that computer).

Windows NT 4.0 Services

• Alerter
• ClipBook Server
• Computer Browser
• Directory Replicator
• Event Log
• Messenger
• Net Logon
• Network DDE
• Network DDE DSDM
• NT LM Security Support Provider
• Remote Procedure Call (RPC) Locator
• Remote Procedure Call (RPC) Service
• Schedule
• Server
• Spooler
• UPS
• Workstation

Windows 2000 Services

• Alerter
• Computer Browser
• Distributed File System
• Distributed Link Tracking Client
• Distributed Link Tracking Server
• DNS Client
• Event Log
• IPSEC Policy Agent
• License Logging Service
• Logical Disk Manager
• Messenger
• Net Logon
• NT LM Security Support Provider
• Network Connectors
• Plug and Play
• Process Control
• Remote Procedure Call (RPC) Locator
• Remote Procedure Call (RPC) Service
• Remote Registry Service
• Removable Storage
• RunAs Service
• Security Accounts Manager
• Server
• Spooler
• TCP/IP NetBIOS Helper
• Time Service
• Windows Management Instrumentation Driver Extensions
• Windows Time
• Workstation

For more information about TCP/IP, see the "Microsoft Windows 2000 TCP/IP Implementation Details" white paper: Portqry.exe is a command-line utility that you can use to help troubleshoot TCP/IP connectivity issues. Portqry.exe runs on Windows 2000-based computers. The utility reports the port status of TCP and UDP ports on a computer that you choose. For additional information about the Portqry.exe command-line utility, click the article numbers below to view the articles in the Microsoft Knowledge Base: In certain circumstances, the error message might occur because of the bug described in the following Microsoft Knowledge Base article: