Microsoft KB Archive/263823

= WinSock Recvfrom now returns WSAECONNRESET instead of blocking or timing out =

Article ID: 263823

Article Last Modified on 2/21/2007

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APPLIES TO


 * Microsoft Windows 2000 Server
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Professional Edition

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This article was previously published under Q263823



SYMPTOMS
In Windows 2000, a User Datagram Protocol (UDP) program may not work and may generate a WSAECONNRESET response.



CAUSE
If sending a datagram using the sendto function results in an &quot;ICMP port unreachable&quot; response and the select function is set for readfds, the program returns 1 and the subsequent call to the recvfrom function does not work with a WSAECONNRESET (10054) error response. In Microsoft Windows NT 4.0, this situation causes the select function to block or time out.



RESOLUTION
To resolve this problem, obtain the latest service pack for Windows 2000. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

260910 How to obtain the latest Windows 2000 service pack

A new sockets IOCTL called &quot;SIO_UDP_CONNRESET&quot; has been introduced in Windows 2000. When this IOCTL is used, the program must be rewritten specifically for Windows 2000 to obtain the original Windows NT 4.0 behavior. Windows NT 4.0, Microsoft Windows 95, and Microsoft Windows 98 have no support for this new IOCTL. In addition to rewriting your application, you will need the hotfix referenced further down in this article.

The following code snippet demonstrates a technique that can be used to call WSAIoctl with the SIO_UDP_CONNRESET control code to obtain the original Windows NT 4.0 behavior. DWORDdwBytesReturned = 0; BOOLbNewBehavior = FALSE; DWORDstatus;

// disable new behavior using // IOCTL: SIO_UDP_CONNRESET status = WSAIoctl(sd, SIO_UDP_CONNRESET, &bNewBehavior, sizeof(bNewBehavior),                  NULL, 0, &dwBytesReturned,                   NULL, NULL);

if (SOCKET_ERROR == status) { DWORD dwErr = WSAGetLastError; if (WSAEWOULDBLOCK == dwErr) { // nothing to do return(FALSE); } else { printf(&quot;WSAIoctl(SIO_UDP_CONNRESET) Error: %d\n&quot;, dwErr); return(FALSE); } } To be able to compile this code, you need either to have the latest Mswsock.h which includes the definition of SIO_UDP_CONNRESET or to insert below definition of it directly into your code. // MS Transport Provider IOCTL to control // reporting PORT_UNREACHABLE messages // on UDP sockets via recv/WSARecv/etc. // Path TRUE in input buffer to enable (default if supported), // FALSE to disable. Note The hotfix that is described in this article will not resolve the problem unless the program is rewritten to use the new SIO_UDP_CONNRESET IOCTL.
 * 1) defineSIO_UDP_CONNRESET_WSAIOW(IOC_VENDOR,12)

In order to compile this code, it is necessary to have the latest Platform SDK installed on your computer. This is available from the following MSDN Web site:

http://msdn.microsoft.com



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Windows 2000 Service Pack 2.



MORE INFORMATION
For more information about how to install Windows 2000 and Windows 2000 hotfixes at the same time, click the following article number to view the article in the Microsoft Knowledge Base:

249149 Installing Microsoft Windows 2000 and Windows 2000 hotfixes

Keywords: kbhotfixserver kbqfe kbbug kbfix kbwin2000presp2fix KB263823

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