Networking - Java Examples in a Nutshell - page 90

Example 5•4: HttpClient.java (continued)
public class HttpClient {
public static void main(String[] args) {
try {
// Check the arguments
if ((args.length != 1) && (args.length != 2))
throw new IllegalArgumentException("Wrong number of args");
// Get an output stream to write the URL contents to
OutputStream to_file;
if (args.length == 2) to_file = new FileOutputStream(args[1]);
else to_file = System.out;
// Now use the URL class to parse the user-specified URL into
// its various parts.
URL url = new URL(args[0]);
String protocol = url.getProtocol();
if (!protocol.equals("http")) // Check that we support the protocol
throw new IllegalArgumentException("Must use 'http:' protocol");
String host = url.getHost();
int port = url.getPort();
if (port == -1) port = 80; // if no port, use the default HTTP port
String filename = url.getFile();
// Open a network socket connection to the specified host and port
Socket socket = new Socket(host, port);
// Get input and output streams for the socket
InputStream from_server = socket.getInputStream();
PrintWriter to_server = new PrintWriter(socket.getOutputStream());
// Send the HTTP GET command to the Web server, specifying the file
// This uses an old and very simple version of the HTTP protocol
to_server.print("GET " + filename + "\n\n");
to_server.flush(); // Send it right now!
// Now read the server's response, and write it to the file
byte[] buffer = new byte[4096];
int bytes_read;
while((bytes_read = from_server.read(buffer)) != -1)
to_file.write(buffer, 0, bytes_read);
// When the server closes the connection, we close our stuff
socket.close();
to_file.close();
}
catch (Exception e) { // Report any errors that arise
System.err.println(e);
System.err.println("Usage: java HttpClient <URL> [<filename>]");
}
}
}