Java in a Nutshell, 5th Edition

Networking with java.net

The java.net package defines a number of classes that make writing networked applications surprisingly easy. Various examples follow.

Networking with the URL Class

The easiest networking class to use is URL, which represents a uniform resource locator. Different Java implementations may support different sets of URL protocols, but, at a minimum, you can rely on support for the http://, ftp://, and file:// protocols. As of Java 1.4, secure HTTP is also supported with the https:// protocol. Here are some ways you can use the URL class:

import java.net.*;  
import java.io.*;   

// Create some URL objects 
URL url=null, url2=null, url3=null;
try {
  url = new URL("http://www.oreilly.com");        // An absolute URL
  url2 = new URL(url, "catalog/books/javanut4/"); // A relative URL
  url3 = new URL("http:", "www.oreilly.com", "index.html");
} catch (MalformedURLException e) { /* Ignore this exception */ }

// Read the content of a URL from an input stream
InputStream in = url.openStream();

// For more control over the reading process, get a URLConnection object
URLConnection conn = url.openConnection();

// Now get some information about the URL
String type = conn.getContentType();
String encoding = conn.getContentEncoding();
java.util.Date lastModified = new java.util.Date(conn.getLastModified());
int len = conn.getContentLength();

// If necessary, read the contents of the URL using this stream
InputStream in = conn.getInputStream();

Working with Sockets

Sometimes you need ...