The Netbios networking APIs under Windows 9x and NT are a mess. To start with, many of them are not implemented under 9x. Although you may be able to link your program without problem, many of the APIs return 120 ERROR_CALL_NOT_IMPLEMENTED:This function is not supported on this system. More frustrating is that many of the APIs that are implemented return pointers to different types of structures on 9x and NT. Much of the documentation around these APIs is either misleading, flat out wrong, or missing. Many of the APIs are listed as being obsolete while no replacement for their functionality has been provided, yet several programs that come with windows like NetWatch.exe, and Net.exe, and NBTstat.exe clearly use these APIs which supposedly are only available for lazy programmers who don't want to rewrite their apps for the win32 API spec. Under NT most of the Net* functions are declared as accepting character pointers but in fact they want Unicode strings. The same is true for many of the structures returned, their members are declared as being pointers to character strings when in fact they are unicode strings. Some of the APIs are just plain misdeclared.

For any of these APIs to work on a remote target machine, that machine must have the Netbios protocol installed and bound to the adapter which you are communicating on. Most of the Net*Enum APIs require that the server service be running, and many others rely on specific other services (like the messenger service) to be able to retrieve data. All of these programs may only run under NT. There is also a registry entry which can be set to further restrict what information can be retrieved anonymously.


NBTstat.exe uses the Netbios() API to (among other things) send Netbios NAME packets on udp port 137 to an IP address to retrieve the remote adapter status of a Netbios interface. It also retrieves the names in the remote name table, which applications have registered as listening on. Netbios names are 15 characters followed by a 16th binary value, and each names is registered as being either unique or a group name. Many names are standardly registered by specific apps, and by viewing the remote name list you can find out information about what software and services are running on the computer, configuration information such as the machine name, domain name and the name of the currently logged in user. Also returned by the Netbios adapter status call is the MAC address of the remote network adapter. If the "adapter" is actually a modem or other type of dialup access, the address will be listed as 44-45-53-54-00-00 which in ascii spells out "DEST". If the adapter is a NIC, the MAC address is the manufacturer assigned globally unique ID. Apparently NIC manufacturers have started providing software with the hardware that allows you to change this ID arbitrarily. For more information how what this program may be useful for check the Microsoft documentation on the Netbios() API.

NetB.exe is a tool I have written which is basically a commandline wrapper around the Netbios() API. It's most useful command is ASTAT which retrieves the remote adapter status. Although most of the information returned in this structure is left empty, there is still a good deal of information available. In cases where no names are registered it will still display the MAC address unlike NBTStat.exe which simply returns "Host not found." Another problem with NBTstat.exe is that it uses some faulty logic to decide what adapter to send the packets on, so if you have more than one adapter (for instance a network card and a dialup connection) it will not function properly. You must select the correct adapter number to use with NetB.exe using the /A option. The adapter numbers correspond to the Lana Number values in Control Panel-Network-Services-Netbios Interface-Properties.

The usage for NetB.exe is:

NetB v.93 - Questions, comments, bitches and bugs to
netb [Arguments]  [localname] [remotename]
  /A AdapterNum   - Use adapter number AdapterNum (def 0)
  /G              - Local name is a group name
  /S              - SMB Relay mode
  /P              - Pause before exit (holds added name till exit)
  /W WaitMS       - Wait WaitMS milleseconds after EOF for final reads
  /?              - This help
  ADDNAME         - Add a name to the local name table
  ASTAT           - Adapter status
  DGRECV          - Receive a datagram
  DGRECVBC        - Receive a broadcast datagram
  DGSEND          - Send a datagram
  DGSENDBC        - Send a broadcast datagram
  ENUM*           - Enumerate LAN adapters
  FINDNAME        - Find a name on the network
  LISTEN          - Listens for connections
  CALL            - Connect to a remote NetBIOS name
     (* NT Only)
 Note: Machine names are either a < 16 char netbios name or an IP address.
       The binary 16th char can be set by adding \xx to the end of the name
       where xx is the hex value.  Default is 0. * is a special wildcard name.

When using the LISTEN or CALL commands, NetB supports input from either the console or a file via redirection. When using console input, entering of the data to send begins when you begin typing, and the data is sent when a CR is entered. NetB will exit when a CONTROL-Z is entered on a line of its own. When using file input, the /S option can be used to have data sent in SMB packets if the input file is formatted properly. It will send each packet and wait for a response. If used with the LISTEN command, it will first wait for a packet from the client and send responses.

Get SOURCE here
Additional source file with all the MAC prefix manufacturer names
Get BINARY here

Net*Enum() APIs and NULL sessions

Many of the Net* APIs are documented as having been replaced by WNet* functions, yet many of them accomplish things which can not be done with their corresponding WNet function. Furthermore, there are many documentation errors relating to these functions about what security access is required to call the APIs at what levels, and Windows has had several bugs found (mostly pre SP3) relating to what information levels can be returned to anonymous remote users. Although you can not do "net view" on an NT or 2k machine normally, if you first connect with a NULL session (username NULL and password NULL) the remote machine treats you as an anonymous browser. To connect with a NULL session from the commandline in NT use:

net use /user:"" \\MachineNameOrIP ""

Now not only can you do a "net view" you can execute a number of APIs which return information about the remote machine:

GetServerInfo() - displays info about the remote machine including OS type, comment, and flags
NetWkstaGetInfo() - displays info about remote machine including name and domains
NetWkstaUserEnum() - displays the users logged into the remote machine
NetShareEnum()  - displays hidden shares as well (shares ending in $)
NetUserEnum()   - displays users including their Full name, description, type etc
NetRemoteTOD()  - displays the remote clock and uptime
NetTransportEnum() - displays remote information for NICs bound to NETBIOS including MAC addresses
NetEnumerateTrustedDomains() - displays other domains that are trusted by the target machine's
NetServerTransportEnum() - displays the name and MAC address of the adapters Netbios is bound to
NetLocalGroupEnum() - displays remote local groups, their description and their members
NetGroupEnum()  - displays remote global groups and their members
NetServerEnum() - displays machines in the remote browse list (visible Netbios machines)
NetSessionEnum()- displays user and machine name for connections to remote server

There are also many other APIs which may require more access than a NULL session. NetE.exe is a utility I have written which calls one or more of the APIs that return remote information at each of their valid levels until data is retrieved. NetE returns a LOT of information, so to see it I reccomend either redirecting the output to a file or making your console window very large (I typically do "mode 80,5000" so I have a scroll back buffer for the command prompt). For machines with lots of users or shares, there may be long pauses while the data is transfered, especially if that data is being transfered across a slow network connection (like the internet).

The usage for NetE.exe is:

NetE v1.0  Questions, comments, bitches and bugs to

Usage: NetE [Options] \\MachinenameOrIP
 /0 - All NULL session operations
 /* - All operations
 /A - Workstation users
 /B - Get PDC name
 /C - Connections
 /D - Date and time
 /E - Exports
 /F - Files
 /G - Groups
 /H - Workstation transports
 /I - Statistics
 /J - Scheduled jobs
 /K - Disks
 /L - Local groups
 /M - Machines
 /N - Message names
 /O - Server info
 /P - Printer ports and info
 /Q - Platform specific info
 /R - Replicated directories
 /S - Sessions
 /T - Transports
 /U - Users
 /V - Services
 /W - RAS ports
 /X - Uses
 /Y - Remote registry trees
 /Z - Trusted domains

*NOTE* To compile this program you need to correct an error in the lmaccess.h header file that is distributed with the Win32 sdk or MSVC. The API NetEnumerateTrustedDomains() is declared as:

 NetEnumerateTrustedDomains (
and it should be:
 NetEnumerateTrustedDomains (

Get Source HERE.
Get Binary HERE.

Other great sources for much of the same information and more: