DOCUMENT:Q197511  10-AUG-2001  [winnt]
TITLE   :UDP Broadcast Issues with Service Pack 4
PRODUCT :Microsoft Windows NT
PROD/VER:WINNT:4.0
OPER/SYS:
KEYWORDS:

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The information in this article applies to:

 - Microsoft Windows NT Workstation version 4.0 
 - Microsoft Windows NT Server version 4.0 
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SUMMARY
=======

When you apply Service Pack 4 for Windows NT version 4.0, TCP/IP, Windows
Sockets, and Simple TCP/IP services are modified to be resistant to attack. This
modification may cause a loss of functionality in programs that use User
Datagram Protocol (UDP) broadcasts.


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

Because of the security issues fixed in Service Pack 4, the default behavior of
Winsock sockets has been changed. Sockets now receive broadcast datagrams such
as UDP broadcasts only if they have been explicitly set to do so. Prior to these
fixes, any program that issued a Recvfrom() call would receive broadcast
datagrams.

Programs affected by this change should be modified to operate as expected with
Windows NT 4.0 Service Pack 4 or later.


REFERENCES
==========

Winsock supports a socket option (SO_BROADCAST) that can be set to allow the
Recvfrom() call to pass broadcast datagrams to the program. The default setting
for this option is "Off." More information about the SO_BROADCAST option and the
functions used to set socket options is documented in the Platform Software
Development Kit (SDK), which is available online at the following Microsoft Web
site:

   http://msdn.microsoft.com.

Additional query words: simptcp

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Keywords          :  
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400
Version           : WINNT:4.0
Issue type        : kbinfo

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