A Non-Blocking Socket Channel Echo Server Program - Java Network

Java examples for Network:Socket Channel

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Description

A Non-Blocking Socket Channel Echo Server Program

Demo Code

import java.io.IOException;
import java.net.InetAddress;
import java.net.InetSocketAddress;
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.util.Iterator;
import java.util.Set;

public class Main {
  public static void main(String[] args) throws Exception {
    InetAddress hostIPAddress = InetAddress.getByName("localhost");
    int port = 19000;

    Selector selector = Selector.open();

    ServerSocketChannel ssChannel = ServerSocketChannel.open();

    ssChannel.configureBlocking(false);/*from ww w  . j  a  v  a 2s . com*/
    ssChannel.socket().bind(new InetSocketAddress(hostIPAddress, port));

    ssChannel.register(selector, SelectionKey.OP_ACCEPT);

    while (true) {
      if (selector.select() <= 0) {
        continue;
      }
      processReadySet(selector.selectedKeys());
    }
  }

  public static void processReadySet(Set readySet) throws Exception {
    SelectionKey key = null;
    Iterator iterator = null;
    iterator = readySet.iterator();
    while (iterator.hasNext()) {
      key = (SelectionKey) iterator.next();
      iterator.remove();
      if (key.isAcceptable()) {
        processAccept(key);
      }

      if (key.isReadable()) {
        String msg = processRead(key);
        if (msg.length() > 0) {
          echoMsg(key, msg);
        }
      }
    }
  }

  public static void processAccept(SelectionKey key) throws IOException {
    ServerSocketChannel ssChannel =  (ServerSocketChannel)key.channel();
    SocketChannel sChannel = (SocketChannel) ssChannel.accept();
    sChannel.configureBlocking(false);
    sChannel.register(key.selector(), SelectionKey.OP_READ);
  }

  public static String processRead(SelectionKey key) throws Exception {
    SocketChannel sChannel = (SocketChannel) key.channel();
    ByteBuffer buffer = ByteBuffer.allocate(1024);
    int bytesCount = sChannel.read(buffer);
    String msg = "";

    if (bytesCount > 0) {
      buffer.flip();
      Charset charset = Charset.forName("UTF-8");
      CharsetDecoder decoder = charset.newDecoder();
      CharBuffer charBuffer = decoder.decode(buffer);
      msg = charBuffer.toString();
      System.out.println("Received Message: " + msg);
    }

    return msg;
  }

  public static void echoMsg(SelectionKey key, String msg) throws IOException {
    SocketChannel sChannel = (SocketChannel) key.channel();
    ByteBuffer buffer = ByteBuffer.wrap(msg.getBytes());
    sChannel.write(buffer);
  }
}

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