The following warning is often seen on servers running Microsoft Host Integration Server:

Log Name:      Application
Source:        SNA Base Service
Date:          date
Event ID:      561
Task Category: None
Level:         Warning
Keywords:      Classic
User:          user
Computer:      computer
Write to mailslot or socket failed, rc = 64


 A Win32 WriteFile() or winsock sendto() call failed. The return code is shown.


 Provide network support personnel with the event log file(s) related to SNA, and the return code included in this message. For information about SNA log files, see the “Microsoft Host Integration Server Online Books.

 The warning is caused because Host Integration Server tries to communicate with all the servers in a subdomain (and the clients) via broadcasts messages. Host Integration Server does this over all protocols that are selected in the SNA Manager. Not all of these protocols are enabled on your network, if one of them is not enabled this warning will pop up.

To fix this warning unselect the protocol that causes the warning as shown in this screenshot.


Typically you enable TCP/IP and you disable Named Pipes. After adapting the configuration the warning disappears.


Peter Borremans