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

Java examples for Network:Socket Channel

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Description

A Non-Blocking Socket Channel Echo Client Program

Demo Code

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
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.SocketChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.util.Iterator;
import java.util.Set;

public class Main {
  private static BufferedReader userInputReader = null;

  public static void main(String[] args) throws Exception {
    InetAddress serverIPAddress = InetAddress.getByName("localhost");
    int port = 19000;
    InetSocketAddress serverAddress = new InetSocketAddress(serverIPAddress, port);

    Selector selector = Selector.open();

    SocketChannel channel = SocketChannel.open();
    channel.configureBlocking(false);/*from w  w w .j a v a2  s.  c om*/
    channel.connect(serverAddress);

    int operations =
      SelectionKey.OP_CONNECT | SelectionKey.OP_READ | SelectionKey.OP_WRITE;
    channel.register(selector, operations);

    userInputReader = new BufferedReader(new InputStreamReader(System.in));
    while (true) {
      if (selector.select() > 0) {
        boolean doneStatus = processReadySet(selector.selectedKeys());
        if (doneStatus) {
          break;
        }
      }
    }

    channel.close();
  }

  public static boolean 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.isConnectable()) {
        boolean connected = processConnect(key);
        if (!connected) {
          return true;
        }
      }

      if (key.isReadable()) {
        String msg = processRead(key);
        System.out.println("[Server]: " + msg);
      }

      if (key.isWritable()) {
        String msg = getUserInput();
        if (msg.equalsIgnoreCase("bye")) {
          return true; // Exit
        }
        processWrite(key, msg);
      }

    }

    return false;
  }

  public static boolean processConnect(SelectionKey key) {
    SocketChannel channel = (SocketChannel) key.channel();

    try {
      while (channel.isConnectionPending()) {
        channel.finishConnect();
      }
    }
    catch (IOException e) {
      key.cancel();
      e.printStackTrace();
      return false;
    }

    return true;
  }

  public static String processRead(SelectionKey key) throws Exception {
    SocketChannel sChannel = (SocketChannel) key.channel();
    ByteBuffer buffer = ByteBuffer.allocate(1024);
    sChannel.read(buffer);
    buffer.flip();
    Charset charset = Charset.forName("UTF-8");
    CharsetDecoder decoder = charset.newDecoder();
    CharBuffer charBuffer = decoder.decode(buffer);
    String msg = charBuffer.toString();
    return msg;
  }

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

  public static String getUserInput() throws IOException {
    String promptMsg = "Please enter a message(Bye to quit): ";
    System.out.print(promptMsg);
    String userMsg = userInputReader.readLine();
    return userMsg;
  }
}

Result


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