NetBIOS over TCP/IP

The following TCP and UDP ports are used in NetBT, the Windows NT implementation of NetBIOS over TCP/IP.

• UDP port 137 (name services)
• UDP port 138 (datagram services)
• TCP port 139 (session services)

NetBIOS over TCP/IP is specified by RFC 1001 and RFC 1002. The Netbt.sys driver is a kernel-mode component that supports the TDI interface. Services such as Windows NT Workstation and Windows NT Server services use the TDI interface directly, while traditional NetBIOS programs have their calls mapped to TDI calls by using the Netbios.sys driver. Using TDI to make calls to NetBT is a more difficult programming task, but can provide higher performance and freedom from historical NetBIOS limitations.

See the section "Network Application Interfaces" later in this chapter for more information about NetBIOS.