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: ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Workstation version 4.0 - Microsoft Windows NT Server version 4.0 ------------------------------------------------------------------------------- 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 ====================================================================== Keywords : Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 Version : WINNT:4.0 Issue type : kbinfo ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2001.