[TCP/IP User Protocols]


NetBIOS is an acronym for Network Basic Input/Output System. The NetBIOS API allows applications on separate computers to communicate over a local area network. It provides services related to the session layer of the OSI model.

The default NetBIOS name for the Modtronix SBC65EC Web Server is "MXBOARD". This name can be used in stead of the board's IP address in many programs. For example, to access the web based interface of the board, type "http://mxboard" in the address field of a web browser. The following description of NetBIOS was taken from Wikipedia, the free encyclopedia. The Modtronix SBC65EC Web Server only implements a small part of the protocol!


NetBIOS provides three distinct services:

Note: SMB, an upper layer, is a service that runs on top of the Session Service and the Datagram service, and is not to be confused as a necessary and integral part of NetBIOS itself. It can now run atop TCP with a small adaptation layer that adds a packet length to each SMB message; this is necessary because TCP only provides a byte-stream service with no notion of packet boundaries.

Name Service

In order to start Sessions or distribute Datagrams, an application must register its NetBIOS name using the Name service. NetBIOS names are 16 bytes in length and vary based on the particular implementation. Frequently, the 16th byte is used to designate a "type" similar to the use of ports in TCP/IP. In NBT, the name service operates on UDP port 137 (TCP port 137 can also be used, but it is rarely if ever used).

The name service primitives offered by NetBIOS are:

Session Service

Session mode lets two computers establish a connection for a "conversation," allows larger messages to be handled, and provides error detection and recovery. In NBT, the session service runs on TCP port 139.

The session service primitives offered by NetBIOS are:

In the original protocol used to implement NetBIOS services on PC-Network, to establish a session, the computer establishing the session sends an Open request which is responded to by an Open acknowledgment. The computer that started the session will then send a Session Request packet which will prompt either a Session Accept or Session Reject packet. Data is transmitted during an established session by data packets which are responded to with either acknowledgment packets (ACK) or negative acknowledgment packets (NACK). Since NetBIOS is handling the error recovery, NACK packets will prompt retransmission of the data packet. Sessions are closed by the non-initiating computer by sending a close request. The computer that started the session will reply with a close response which prompts the final session closed packet.

Datagram Distribution Service

Datagram mode is "connectionless". Since each message is sent independently, they must be smaller; the application becomes responsible for error detection and recovery. In NBT, the datagram service runs on UDP port 138.

The datagram service primitives offered by NetBIOS are:


For details on configuring this module, see Configuration section of nbns.h file.

Generated on Mon Oct 9 13:22:09 2006 for SBC65EC Web Server by  doxygen 1.4.7