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Q244823: BUG: Numeric Hostnames Use Winsock Control Resolve Improperly

Article: Q244823
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:5.0,6.0
Operating System(s): 
Keyword(s): kbnetwork kbAPI kbCtrl kbSDKPlatform kbSDKWin32 kbVBp500 kbVBp600 kbDSupport kbGrpDSNet
Last Modified: 24-JUL-2000

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The information in this article applies to:

- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
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SYMPTOMS
========

If a computer has a hostname that is all numerals, or if the local computer name
is all numerals, the Winsock Control will not function properly in two cases:

- If you attempt to connect to a hostname that is all numerals, the name will
  not be resolved to a real IP Address, therefore the connection will never be
  made.

- If the local computer's hostname is all numerals, the LocalIP property
  returns what appears to be an invalid IP Address.

If the local computer name is a numeric name, the Winsock Control LocalIP
property returns an incorrect IP address. It will actually return the numeric
named in dotted notation versus doing a real-name lookup on the name.

For example, if a computer name is named "1234567" then LocalIP returns
0.18.214.135. This potentially breaks applications when you use the bind method
on the LocalIP property in certain situations.

The reason for having a computer name of all numerals is for large installations
that use it as a serial number. This is not a problem on Windows 2000 since it
does not allow numeric computer names, however it would present a problem if
trying to connect to a host with a numeric name.

CAUSE
=====

The Winsock Control tries to intelligently resolve names by using the
inet_ntoa() Winsock API call to first try converting the name into an IP
Address. If that succeeds, normal name resolution through gethostbyname() is
bypassed.

The Winsock API inet_ntoa() call given a value returns the dotted notation of the
value. Therefore, a numeric hostname or local computer name will not get
resolved to its true IP Address, but rather a dotted representation of the
numeric name. So for example, if a computer is named "1234567", inet_ntoa()
returns 0.18.214.135.

RESOLUTION
==========

The only resolution is to use non-numeric hostnames or computer names with the
Winsock Control, or use the Winsock API to resolve the names through the Winsock
API SDK calls gethostname()/gethostbyname().

For additional information on using these calls in Visual Basic, click the
article numbers below to view the articles in the Microsoft Knowledge Base:

  Q160215 HOWTO: Obtain the Host IP Address Using Windows Sockets

  Q154512 SAMPLE: WINSOCK.EXE Getting HostAddress Using Windows Sockets

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

MORE INFORMATION
================

Some customer installations name the computers according to an asset tag or
serial number that is all numerals. It is in these cases the problem manifests
itself.

Steps to Reproduce Behavior
---------------------------

1. Using the Network Identification tab of the Network Control Panel, set the
  computer name to all numerals (for example, "1234567")

2. Using Visual Basic, create a new project.

3. Add the Winsock Control as a component and place on the main form.

4. Add the following to the form's code module:

  Option Explicit

  Private Sub Form_Load()
    MsgBox Winsock1.LocalIP
  End Sub

5. Run the program and you will notice the program displays the wrong Local IP
  Address

REFERENCES
==========

For more information, please refer to:

- Microsoft Visual Basic Documentation for the Winsock Control

- Platform SDK: Windows Sockets Version 2

Additional query words:

======================================================================
Keywords          : kbnetwork kbAPI kbCtrl kbSDKPlatform kbSDKWin32 kbVBp500 kbVBp600 kbDSupport kbGrpDSNet 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVB500 kbVB600
Version           : WINDOWS:5.0,6.0
Issue type        : kbbug
Solution Type     : kbnofix

=============================================================================

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