As you probably know, NIO offers many advantages?like speed and a large number of concurrent connections:
import java.io.*;import java.net.*;import java.nio.*;import java.util.*;import java.nio.channels.*;import java.nio.charset.*;public class ServerNIO{ public static void main(String[] args){ ServerSocketChannel serverNIO=null; InetSocketAddress ISA=null; Selector selector=null; ByteBuffer clientBuf=null; int port=5000;try{ serverNIO=ServerSocketChannel.open(); serverNIO.configureBlocking(false); }catch(IOException e) {System.out.println(e.getMessage());} try{ InetAddress addr=InetAddress.getByName("localhost"); ISA=new InetSocketAddress(addr,port); }catch(UnknownHostException e) {System.out.println(e.getMessage());}try{ ServerSocket SS=serverNIO.socket(); SS.bind(ISA); System.out.println("- Ready -"); }catch(IOException e) {System.out.println(e.getMessage());}try{ selector=Selector.open(); serverNIO.register(selector,SelectionKey.OP_ACCEPT); }catch(IOException e) {System.out.println(e.getMessage());} while(true) {try{ selector.select(); }catch(IOException e) {System.out.println(e.getMessage());} Set keys=selector.selectedKeys(); Iterator iter=keys.iterator(); while(iter.hasNext()) { SelectionKey key=(SelectionKey)iter.next(); iter.remove(); if((key.isValid())&&(key.isAcceptable())) { try{ ServerSocketChannel SSC=(ServerSocketChannel)key.channel(); SocketChannel clientNIO=SSC.accept(); clientNIO.configureBlocking(false); SelectionKey SK=clientNIO.register( selector,SelectionKey.OP_READ | SelectionKey.OP_WRITE); }catch(IOException e) {System.out.println(e.getMessage());} } if((key.isValid())&&(key.isReadable())) { try{ SocketChannel clientNIO=(SocketChannel)key.channel(); clientBuf=ByteBuffer.allocateDirect(1024); clientNIO.read(clientBuf); }catch(IOException e) {System.out.println(e.getMessage()); try{ key.channel().close();key.cancel(); }catch(IOException ex) {System.out.println(e.getMessage());}} clientBuf.flip(); Charset charset=Charset.forName("ISO-8859-1"); CharsetDecoder decoder = charset.newDecoder(); try{ CharBuffer charBuffer = decoder.decode(clientBuf); System.out.println(charBuffer.toString()); clientBuf.clear(); }catch(IOException e) {System.out.println(e.getMessage());} } if((key.isValid())&&(key.isWritable())) { SocketChannel clientNIO=(SocketChannel)key.channel(); ByteBuffer serverBuf=ByteBuffer.allocateDirect(1024); try{ String s="Message from server ..."; serverBuf.put(s.getBytes()); serverBuf.flip(); clientNIO.write(serverBuf); }catch(IOException e) {System.out.println(e.getMessage()); try{ key.channel().close();key.cancel(); }catch(IOException ex) {System.out.println(ex.getMessage());}} } } } } }
