c# qr code generator dll Lesson 1 in C#

Making QR Code JIS X 0510 in C# Lesson 1

In the early eighties, Sytek Corporation developed NetBIOS for IBM to enable their applications to communicate over a network. After twenty years, many applications are still using NetBIOS. Previous versions of Windows used NetBIOS names to identify resources that were on a network. A NetBIOS name is a 16-byte address used to identify a network resource, just as a host name identifies resources on a TCP/IP network. The first 15 characters of the NetBIOS name are specified by the administrator, and the 16th character, a hexadecimal number, is reserved to indicate the resource type. Most people refer to the name they give their workstation as the computer name. This, in fact, is the NetBIOS name, which can be used by other workstations to access it. See Table 7-1 and Table 7-2 for examples of NetBIOS names used by various Microsoft components.

Table 7-1

Description WINS client registration of computer name done by Workstation service Registered by the Messenger service of the WINS client Registered by the Server service on the WINS client The username registered by the Messenger service, which allows the user to receive net send commands

Unique names computer_name[00h ] computer_name[03h] computer_name[20h] username[03h]

Table 7-2

Description Registered by the Domain Controllers within the domain Registered by the Master Browser for each subnet Used by browsers to elect a Master Browser

Group names domain_name[1Ch] __MSBROWSE__[01h] domain_name[1Eh]

To access a share called Payroll on a computer with a NetBIOS name of HR_Director, you would type \\hr_director\payroll at the Run command prompt. Your workstation would broadcast the name hr_director[20h] on the local area network (LAN) segment so it could get the IP address of the target workstation. See Figure 7-1.

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Broadcast Not me!

As you can see from Figure 7-1, all workstations that receive the name resolution broadcast message are asked if they own the NetBIOS name hr_director[20h]. The workstation configured with the computer name of hr_director will then respond to the workstation requesting it. The problem with this scenario is that broadcast traffic was needed to perform the NetBIOS name resolution. Broadcast traffic, sometimes a necessary evil in networks, must be sent to every port on a network, and as a result can slow down your network. Network administrators try to reduce broadcast traffic as much as possible. WINS is one of the ways to do this. Creating an Lmhosts file is one remedy covered in this section. Adding routers to a network segment is another, and will be covered in more detail in 8, Designing a Network and Routing Infrastructure. Which method a client uses to execute name resolution is determined by a node type. See Table 7-3 for the node types available for NetBIOS name resolution.

Table 7-3

Name resolution mode Description B-node P-node M-node Uses broadcast messages to register NetBIOS names or resolve NetBIOS names to IP addresses Uses unicast to directly communicate with a NetBIOS name server (WINS) to register or resolve NetBIOS names Uses broadcast (B-node) first when attempting to register or resolve a NetBIOS name, and then queries a WINS server (P-node) if unsuccessful with the broadcast. The M stands for mixed because it uses a mix of B-node and P-node. Uses hybrid (h-mode), a combination of P-node and then B-node. In other words, it first communicates with the WINS server to resolve the NetBIOS name and if unsuccessful, attempts a broadcast message.

By default, Windows Server 2003 computers use b-node unless WINS is configured; then h-node is the default node type. For a quick way to see which node type is used by a client, type ipconfig /all at the command prompt of the client s workstation. See