src/java.base/share/classes/java/net/PortUnreachableException.java

*** 31,40 ****
--- 31,41 ----
   *
   * @since   1.4
   */
  
  public class PortUnreachableException extends SocketException {
+     @java.io.Serial
      private static final long serialVersionUID = 8462541992376507323L;
  
      /**
       * Constructs a new {@code PortUnreachableException} with a
       * detail message.