TCP/IP-32 Winsock Stops FD_READ Notification

• Microsoft TCP/IP-32 for Windows for Workgroups, version 3.11

SYMPTOMS

FD_READ notification in a Winsock application may stop while the application is running. This may cause data to be left in the input buffer, or, it may cause the application to hang.

This occurs when the application disables and then re-enables FD_READ notification during a period of time while the Windows message queue is full.

CAUSE

The problem is that WINSOCK.DLL does not retry failed PostMessage attempts.

WINSOCK.DLL posts messages whenever WSAAsyncSelect() is called with interest in events that are already active on a socket. For example, if you call WSAAsyncSelect with the FD_READ bit set on a socket which already had read data waiting, WINSOCK.DLL immediately posts an FD_READ message. When the Windows message queue is full, this PostMessage call fails.

RESOLUTION

Microsoft has released a new file, WSOCK.386, that corrects this problem.

STATUS

Microsoft has confirmed this to be a problem in TCP/IP-32. This problem has been corrected in an updated TCP/IP-32 version 3.11a. For information on the availability of TCP/IP-32 3.11a, see article Q122544 in the Microsoft Knowledge Base.