Java™ Platform
Standard Ed. 7


Provides the classes for implementing networking applications.

See: Description

Package Description

Provides the classes for implementing networking applications.

The package can be roughly divided in two sections:


Addresses are used throughout the APIs as either host identifiers, or socket endpoint identifiers.

The InetAddress class is the abstraction representing an IP (Internet Protocol) address. It has two subclasses:

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.

About IPv6

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 InetAddress.getByName(java.lang.String) 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.


Sockets are means to establish a communication link between machines over the network. The package provides 4 kinds of Sockets:

Sending and receiving with TCP sockets is done through InputStreams and OutputStreams which can be obtained via the Socket.getInputStream() and Socket.getOutputStream() methods.


The 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.

High level API

A number of classes in the package do provide for a much higher level of abstraction and allow for easy access to resources on the network. The classes are:

The recommended usage is to use URI to identify resources, then convert it into a URL when it is time to access the resource. From that URL, you can either get the URLConnection for fine control, or get directly the InputStream.

Here is an example:

URI uri = new URI("");
URL url = uri.toURL();
InputStream in = url.openStream();

Protocol Handlers

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. 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.

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 java.protocol.handler.pkgs system property. For instance if it is set to myapp.protocols, then the URL code will try, in the case of http, first to load myapp.protocols.http.Handler, then, if this fails, http.Handler from the default location.

Note that the Handler class has to be a subclass of the abstract class URLStreamHandler.

Additional Specification

Java™ Platform
Standard Ed. 7

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