Index: doc/SetErrno.3
==================================================================
--- doc/SetErrno.3
+++ doc/SetErrno.3
@@ -6,11 +6,11 @@
 '\"
 .TH Tcl_SetErrno 3 8.3 Tcl "Tcl Library Procedures"
 .so man.macros
 .BS
 .SH NAME
-Tcl_SetErrno, Tcl_GetErrno, Tcl_ErrnoId, Tcl_ErrnoMsg \- manipulate errno to store and retrieve error codes
+Tcl_SetErrno, Tcl_GetErrno, Tcl_ErrnoId, Tcl_ErrnoMsg, Tcl_WinConvertError \- manipulate errno to store and retrieve error codes
 .SH SYNOPSIS
 .nf
 \fB#include <tcl.h>\fR
 .sp
 \fBTcl_SetErrno\fR(\fIerrorCode\fR)
@@ -21,15 +21,21 @@
 const char *
 \fBTcl_ErrnoId\fR()
 .sp
 const char *
 \fBTcl_ErrnoMsg\fR(\fIerrorCode\fR)
+.sp
+void
+\fBTcl_WinConvertError\fR(\fIwinErrorCode\fR)
 .fi
 .SH ARGUMENTS
 .AS int errorCode
 .AP int errorCode in
 A POSIX error code such as \fBENOENT\fR.
+.AS unsigned int winErrorCode in
+.AP DWORD winErrorCode in
+A Windows or Winsock error code such as \fBERROR_FILE_NOT_FOUND\fR.
 .BE
 
 .SH DESCRIPTION
 .PP
 \fBTcl_SetErrno\fR and \fBTcl_GetErrno\fR provide portable access
@@ -58,8 +64,11 @@
 that corresponds to the value of its
 \fIerrorCode\fR argument.  The \fIerrorCode\fR argument is
 typically the value returned by \fBTcl_GetErrno\fR.
 The strings returned by these functions are
 statically allocated and the caller must not free or modify them.
+.PP
+\fBTcl_WinConvertError\fR (Windows only) maps the passed Windows or Winsock
+error code to a POSIX error and stores it in \fBerrno\fR.
 
 .SH KEYWORDS
 errno, error code, global variables

Index: tests/socket.test
==================================================================
--- tests/socket.test
+++ tests/socket.test
@@ -2396,13 +2396,15 @@
     } -result {{} ok}
 test socket-14.11.0 {pending [socket -async] and nonblocking [puts], no listener, no flush} \
     -constraints {socket notWinCI} \
     -body {
         set sock [socket -async localhost [randport]]
+        fileevent $sock writable {incr x}
+        vwait x
         fconfigure $sock -blocking 0
         puts $sock ok
-        fileevent $sock writable {set x 1}
+        fileevent $sock writable {incr x}
         vwait x
         close $sock
     } -cleanup {
         catch {close $sock}
         unset x