NetBIOS Datagrams

Datagrams can be sent to a specific name, sent to all members of a group, or broadcast to
the entire LAN. As with other datagram services, the NetBIOS datagrams are
connectionless and unreliable. The Send_Datagram command requires the caller to
specify the name of the destination. If the destination is a group name, then every
member of the group receives the datagram. The caller of the Receive_Datagram
command must specify the local name for which it wants to receive datagrams. The
Receive_Datagram command also returns the name of the sender, in addition to the actual
datagram data. If NetBIOS receives a datagram, but there are no Receive_Datagram
commands pending, then the datagram is discarded.
The Send_Broadcast_Datagram command sends the message to every NetBIOS system
on the local network. When a broadcast datagram is received by a NetBIOS node, every
process that has issued a Receive_Broadcast_Datagram command receives the datagram.
If none of these commands are outstanding when the broadcast datagram is received, the
datagram is discarded.
NetBIOS enables an application to establish a session with another device and lets the
network redirector and transaction protocols pass a request to and from another machine.
NetBIOS does not actually manipulate the data. The NetBIOS specification defines an
interface to the network protocol used to reach those services, not the protocol itself.
Historically, has been paired with a network protocol called NetBEUI (network extended
user interface). The association of the interface and the protocol has sometimes caused
confusion, but the two are different.
Network protocols always provide at least one method for locating and connecting to a
particular service on a network. This is usually accomplished by converting a node or
service name to a network address (name resolution). NetBIOS service names must be
resolved to an IP address before connections can be established with TCP/IP. Most
NetBIOS implementations for TCP/IP accomplish name address resolution by using
either broadcast or LMHOSTS files. In a Microsoft enviroment, you would probably also
use a NetBIOS Namer Server known as WINS.