Microsoft say this about Winsock error 10004 - WSAEINTR:

A blocking operation was interrupted by a call to WSACancelBlockingCall.

Full details of Winsock TCP error 10004 - WSAEINTR:

Berkeley description: An asynchronous signal (such as SIGINTor SIGQUIT) was caught by the process during the execution of an interruptible function. If the signal handler performs a normal return, the interrupted function call will seem to have returned the error condition.

WinSock description: NOT same as Berkeley, but analogous. In WinSock it means a blocking operation was interrupted by a call to.

Developer suggestions: You need to be prepared to handle this error on any functions that reference blocking sockets, or any calls to blocking functions, if you allow the user to cancel a blocking call. Whether to handle it as a fatal error or non-fatal error depends on the application and the context, so it's entirely up to you to decide.