| /* |
| * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| /** |
| * Provides the classes for implementing networking applications. |
| * |
| * <p> The java.net package can be roughly divided in two sections:</p> |
| * <ul> |
| * <li><p><i>A Low Level API</i>, which deals with the |
| * following abstractions:</p> |
| * <ul> |
| * <li><p><i>Addresses</i>, which are networking identifiers, |
| * like IP addresses.</p></li> |
| * <li><p><i>Sockets</i>, which are basic bidirectional data communication |
| * mechanisms.</p></li> |
| * <li><p><i>Interfaces</i>, which describe network interfaces. </p></li> |
| * </ul></li> |
| * <li> <p><i>A High Level API</i>, which deals with the following |
| * abstractions:</p> |
| * <ul> |
| * <li><p><i>URIs</i>, which represent |
| * Universal Resource Identifiers.</p></li> |
| * <li><p><i>URLs</i>, which represent |
| * Universal Resource Locators.</p></li> |
| * <li><p><i>Connections</i>, which represents connections to the resource |
| * pointed to by <i>URLs</i>.</p></li> |
| * </ul></li> |
| * </ul> |
| * <h2>Addresses</h2> |
| * <p>Addresses are used throughout the java.net APIs as either host |
| * identifiers, or socket endpoint identifiers.</p> |
| * <p>The {@link java.net.InetAddress} class is the abstraction representing an |
| * IP (Internet Protocol) address. It has two subclasses: |
| * <ul> |
| * <li>{@link java.net.Inet4Address} for IPv4 addresses.</li> |
| * <li>{@link java.net.Inet6Address} for IPv6 addresses.</li> |
| * </ul> |
| * <p>But, in most cases, there is no need to deal directly with the subclasses, |
| * as the InetAddress abstraction should cover most of the needed |
| * functionality.</p> |
| * <h3><b>About IPv6</b></h3> |
| * <p>Not all systems have support for the IPv6 protocol, and while the Java |
| * networking stack will attempt to detect it and use it transparently when |
| * available, it is also possible to disable its use with a system property. |
| * In the case where IPv6 is not available, or explicitly disabled, |
| * Inet6Address are not valid arguments for most networking operations any |
| * more. While methods like {@link java.net.InetAddress#getByName} are |
| * guaranteed not to return an Inet6Address when looking up host names, it |
| * is possible, by passing literals, to create such an object. In which |
| * case, most methods, when called with an Inet6Address will throw an |
| * Exception.</p> |
| * <h2>Sockets</h2> |
| * <p>Sockets are means to establish a communication link between machines over |
| * the network. The java.net package provides 4 kinds of Sockets:</p> |
| * <ul> |
| * <li>{@link java.net.Socket} is a TCP client API, and will typically |
| * be used to {@linkplain java.net.Socket#connect(SocketAddress) |
| * connect} to a remote host.</li> |
| * <li>{@link java.net.ServerSocket} is a TCP server API, and will |
| * typically {@linkplain java.net.ServerSocket#accept accept} |
| * connections from client sockets.</li> |
| * <li>{@link java.net.DatagramSocket} is a UDP endpoint API and is used |
| * to {@linkplain java.net.DatagramSocket#send send} and |
| * {@linkplain java.net.DatagramSocket#receive receive} |
| * {@linkplain java.net.DatagramPacket datagram packets}.</li> |
| * <li>{@link java.net.MulticastSocket} is a subclass of |
| * {@code DatagramSocket} used when dealing with multicast |
| * groups.</li> |
| * </ul> |
| * <p>Sending and receiving with TCP sockets is done through InputStreams and |
| * OutputStreams which can be obtained via the |
| * {@link java.net.Socket#getInputStream} and |
| * {@link java.net.Socket#getOutputStream} methods.</p> |
| * <h2>Interfaces</h2> |
| * <p>The {@link java.net.NetworkInterface} class provides APIs to browse and |
| * query all the networking interfaces (e.g. ethernet connection or PPP |
| * endpoint) of the local machine. It is through that class that you can |
| * check if any of the local interfaces is configured to support IPv6.</p> |
| * <p>Note, all conforming implementations must support at least one |
| * {@code NetworkInterface} object, which must either be connected to a |
| * network, or be a "loopback" interface that can only communicate with |
| * entities on the same machine.</p> |
| * |
| * <h2>High level API</h2> |
| * <p>A number of classes in the java.net package do provide for a much higher |
| * level of abstraction and allow for easy access to resources on the |
| * network. The classes are: |
| * <ul> |
| * <li>{@link java.net.URI} is the class representing a |
| * Universal Resource Identifier, as specified in RFC 2396. |
| * As the name indicates, this is just an Identifier and doesn't |
| * provide directly the means to access the resource.</li> |
| * <li>{@link java.net.URL} is the class representing a |
| * Universal Resource Locator, which is both an older concept for |
| * URIs and a means to access the resources.</li> |
| * <li>{@link java.net.URLConnection} is created from a URL and is the |
| * communication link used to access the resource pointed by the |
| * URL. This abstract class will delegate most of the work to the |
| * underlying protocol handlers like http or https.</li> |
| * <li>{@link java.net.HttpURLConnection} is a subclass of URLConnection |
| * and provides some additional functionalities specific to the |
| * HTTP protocol.</li> |
| * </ul> |
| * <p>The recommended usage is to use {@link java.net.URI} to identify |
| * resources, then convert it into a {@link java.net.URL} when it is time to |
| * access the resource. From that URL, you can either get the |
| * {@link java.net.URLConnection} for fine control, or get directly the |
| * InputStream. |
| * <p>Here is an example:</p> |
| * <pre> |
| * URI uri = new URI("http://java.sun.com/"); |
| * URL url = uri.toURL(); |
| * InputStream in = url.openStream(); |
| * </pre> |
| * <h2>Protocol Handlers</h2> |
| * As mentioned, URL and URLConnection rely on protocol handlers which must be |
| * present, otherwise an Exception is thrown. This is the major difference with |
| * URIs which only identify resources, and therefore don't need to have access |
| * to the protocol handler. So, while it is possible to create an URI with any |
| * kind of protocol scheme (e.g. {@code myproto://myhost.mydomain/resource/}), |
| * a similar URL will try to instantiate the handler for the specified protocol; |
| * if it doesn't exist an exception will be thrown. |
| * <p>By default the protocol handlers are loaded dynamically from the default |
| * location. It is, however, possible to add to the search path by setting |
| * the {@code java.protocol.handler.pkgs} system property. For instance if |
| * it is set to {@code myapp.protocols}, then the URL code will try, in the |
| * case of http, first to load {@code myapp.protocols.http.Handler}, then, |
| * if this fails, {@code http.Handler} from the default location. |
| * <p>Note that the Handler class <b>has to</b> be a subclass of the abstract |
| * class {@link java.net.URLStreamHandler}.</p> |
| * <h2>Additional Specification</h2> |
| * <ul> |
| * <li><a href="doc-files/net-properties.html"> |
| * Networking System Properties</a></li> |
| * </ul> |
| * |
| * @since JDK1.0 |
| */ |
| package java.net; |
