Windows: the correct way to make TCP_KEEPALIVE work on MinGW

src/win/tcp.c

@@ -71,7 +71,7 @@ static int uv__tcp_keepalive(uv_tcp_t* handle, SOCKET socket, int enable, unsign
 
   if (enable && setsockopt(socket,
                            IPPROTO_TCP,
-                           SO_KEEPALIVE,
+                           TCP_KEEPALIVE,
                            (const char*)&delay,
                            sizeof delay) == -1) {
     uv__set_sys_error(handle->loop, errno);

src/win/winsock.h

@@ -37,6 +37,10 @@
 # define SO_UPDATE_CONNECT_CONTEXT 0x7010
 #endif
 
+#ifndef TCP_KEEPALIVE
+# define TCP_KEEPALIVE 3
+#endif
+
 #ifndef IPV6_V6ONLY
   #define IPV6_V6ONLY 27
 #endif