Reading Web Pages with Socket Channels

[Java Tip]

This Java tip shows how to read a web server response using Socket channels in Java.

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.UnknownHostException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;

public class GetWebPageDemo {
  public static void main(String args[]) throws Exception {
    String resource, host, file;
    int slashPos;

    resource = "www.java-forums.org"; 
    slashPos = resource.indexOf('/'); // find host/file separator
    if (slashPos < 0) {
      resource = resource + "/";
      slashPos = resource.indexOf('/');
    }
    file = resource.substring(slashPos); // isolate host and file parts
    host = resource.substring(0, slashPos);
    System.out.println("Host to contact: '" + host + "'");
    System.out.println("File to fetch : '" + file + "'");

    SocketChannel channel = null;

    try {
      Charset charset = Charset.forName("ISO-8859-1");
      CharsetDecoder decoder = charset.newDecoder();
      CharsetEncoder encoder = charset.newEncoder();

      ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
      CharBuffer charBuffer = CharBuffer.allocate(1024);

      InetSocketAddress socketAddress = new InetSocketAddress(host, 80);
      channel = SocketChannel.open();
      channel.connect(socketAddress);

      String request = "GET " + file + " \r\n\r\n";
      channel.write(encoder.encode(CharBuffer.wrap(request)));

      while ((channel.read(buffer)) != -1) {
        buffer.flip();
        decoder.decode(buffer, charBuffer, false);
        charBuffer.flip();
        System.out.println(charBuffer);
        buffer.clear();
        charBuffer.clear();
      }
    } catch (UnknownHostException e) {
      System.err.println(e);
    } catch (IOException e) {
      System.err.println(e);
    } finally {
      if (channel != null) {
        try {
          channel.close();
        } catch (IOException ignored) {
        }
      }
    }

    System.out.println("\nDone.");
  }
}