Introduction

Ran into a strange problem with WSS 3.0 that appeared to involve hung sockets, the sql server dynamically assigned port changing, or some other network related problem.  404 errors with some documents in the document libraries, 500 Internal Server errors, memory errors, and tons of sql server related errors in the event logs.

In this particular situation, a reboot resolved all issues but left me wondering how networking worked within the SharePoint product itself.  The following are notes on SharePoint inter-process communications, network communication protocols, ports that SharePoint Server uses during its operation, etc.

SharePoint Network Communications

Overview

SharePoint uses a wide variety of protocols to communicate all of which are described by Microsoft in great detail.  In a nutshell, SharePoint network traffic occurs over these three transport protocols:

SQL Server Tabular Data Stream (TDS)

TDS is an application layer network protocol first created by Sybase. It is used to encapsulate the SQL queries.  All traffic in and out of SQL Server is handled by TDS (see Yellow paths in diagram below).  By default this takes place on port TCP:1433 but named instances of SQL Server (any other database instances running on the server must be named instances – e.g. “myserver\instancename”) will use a dynamically assigned port instead.  The dynamic assignment occurs in a two stage process.  First, the SQL client will call the SQL Server management service on port UDP:1434.  The SQL Server Management service will respond with a dynamic port assignment that will be used for subsequent communications.  The dynamic port assignment itself is generated when the SQL Server instance is first started.  As Microsoft explains:

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 SQL Server clients request SQL Server resources, 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.

Server Message Block (SMB)

SMB, or Common Internet File System (CIFS), is an application layer network protocol mainly used to provide access to printers, file systems, and other miscellaneous communications. It also provides an authenticated inter-process communication mechanism.  SMB is used for search and query operations within SharePoint (see the Red paths in the diagram below). This occurs on port TCP:445 or TCP:137,138,139 (over NetBIOS).

Hypertext Transfer Protocol (HTTP)

As expected, HTTP handles all incoming traffic and web service calls. This will typically occur over ports TCP:80 or TCP:443 for secured SSL communications.  Shared Service Provider (SSP) web service calls occur on ports 56737 and 56738 (SSL).  Share Service Providers are replaced in SharePoint 2010 with Service Applications which use ports 32843, 32844 (HTTPS), 32845 instead.

Other Ports

Other ports that SharePoint could use to communicate to other servers include:

• AD Authentication: Occurs on TCP:445 or TCP:88 (Kerberos)
• LDAP: Occurs on LDAP:389 and LDAPS:636
• DNS: occurs on TCP:53
• SMTP: Occurs on TCP:25

Inter-Server Communications

This is traffic between the servers in the SharePoint farm including the SharePoint boxes and the SQL Server boxes (click drawing for full-size view).

Communication with other servers

This could be communications between SharePoint and Active Directory, DNS, etc.

SharePoint 2007 ports and directions

SharePoint 2010 Ports

SharePoint 2010 uses the same ports as SharePoint 2007 with these additions: