Non block server
import java.io.IOException; import java.nio.ByteBuffer; import java.nio.CharBuffer; import java.nio.channels.SelectionKey; import java.nio.channels.Selector; import java.nio.channels.ServerSocketChannel; import java.nio.channels.SocketChannel; import java.nio.charset.Charset; import java.nio.charset.CharsetDecoder; import java.nio.charset.CharsetEncoder; import java.util.Iterator; import java.util.Set; public class MainClass { public static void main(String[] args) throws IOException { Charset charset = Charset.forName("ISO-8859-1"); CharsetEncoder encoder = charset.newEncoder(); CharsetDecoder decoder = charset.newDecoder(); ByteBuffer buffer = ByteBuffer.allocate(512); Selector selector = Selector.open(); ServerSocketChannel server = ServerSocketChannel.open(); server.socket().bind(new java.net.InetSocketAddress(8000)); server.configureBlocking(false); SelectionKey serverkey = server.register(selector, SelectionKey.OP_ACCEPT); for (;;) { selector.select(); Set keys = selector.selectedKeys(); for (Iterator i = keys.iterator(); i.hasNext();) { SelectionKey key = (SelectionKey) i.next(); i.remove(); if (key == serverkey) { if (key.isAcceptable()) { SocketChannel client = server.accept(); client.configureBlocking(false); SelectionKey clientkey = client.register(selector, SelectionKey.OP_READ); clientkey.attach(new Integer(0)); } } else { SocketChannel client = (SocketChannel) key.channel(); if (!key.isReadable()) continue; int bytesread = client.read(buffer); if (bytesread == -1) { key.cancel(); client.close(); continue; } buffer.flip(); String request = decoder.decode(buffer).toString(); buffer.clear(); if (request.trim().equals("quit")) { client.write(encoder.encode(CharBuffer.wrap("Bye."))); key.cancel(); client.close(); } else { int num = ((Integer) key.attachment()).intValue(); String response = num + ": " + request.toUpperCase(); client.write(encoder.encode(CharBuffer.wrap(response))); key.attach(new Integer(num + 1)); } } } } } }