--- old/src/java.base/share/classes/java/nio/channels/DatagramChannel.java	2020-07-31 12:17:05.000000000 +0100
+++ new/src/java.base/share/classes/java/nio/channels/DatagramChannel.java	2020-07-31 12:17:05.000000000 +0100
@@ -150,6 +150,9 @@
      *
      * @throws  IOException
      *          If an I/O error occurs
+     *
+     * @see     <a href="../../net/doc-files/net-properties.html#Ipv4IPv6">
+     *          java.net.preferIPv4Stack</a> system property
      */
     public static DatagramChannel open() throws IOException {
         return SelectorProvider.provider().openDatagramChannel();
@@ -169,6 +172,9 @@
      * java.nio.channels.spi.SelectorProvider} object.  The channel will not be
      * connected.
      *
+     * @apiNote <a href="package-summary.html#unixdomain">Unix domain</a> sockets
+     * are not supported by DatagramChannel.
+     *
      * @param   family
      *          The protocol family
      *
@@ -182,6 +188,9 @@
      * @throws  IOException
      *          If an I/O error occurs
      *
+     * @see     <a href="../../net/doc-files/net-properties.html#Ipv4IPv6">
+     *          java.net.preferIPv4Stack</a> system property
+     *
      * @since   1.7
      */
     public static DatagramChannel open(ProtocolFamily family) throws IOException {
@@ -629,5 +638,4 @@
      */
     @Override
     public abstract SocketAddress getLocalAddress() throws IOException;
-
 }