ReceiveMultipleMessages.java

import java.util.Iterator;
import java.util.Set;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.ByteBuffer;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;

public class ReceiveMultipleMessages {

    public static void handleConnection() throws Exception {
        // Modify this to match the computer you are connecting to
        String ipAddress = "127.0.0.1";
        int port = 10000;

        // Selector: multiplexor of SelectableChannel objects
        Selector channelSelector = Selector.open(); // selector is open here

        // ServerSocketChannel: selectable channel for stream-oriented listening sockets
        ServerSocketChannel myServerSocketChannel = ServerSocketChannel.open();
        InetSocketAddress myAddress = new InetSocketAddress(ipAddress, port);

        // Binds the channel's socket to a local address and configures the socket to listen for connections
        myServerSocketChannel.bind(myAddress);

        // Adjusts this channel's blocking mode.
        myServerSocketChannel.configureBlocking(false);

        // Used as a 'state machine' for figuring if socket is waiting for a connection,
        // or if we have a connection and instead should be receiving data
        int ops = myServerSocketChannel.validOps();
        SelectionKey selectKy = myServerSocketChannel.register(channelSelector, ops, null);

        // Create variables for receiving the message and keeping stats
        String fullMessage = "";
        boolean done = false;
        int chunks = 0;
        long startTime = System.currentTimeMillis();
        long endTime = 0L;

        System.out.println("\nStarting...");

        while(!done) {

            // Selects a set of keys whose corresponding channels are ready for I/O operations
            // For blocking I/O use a select with no data:
            // channelSelector.select(10);
            // For non-blocking, use a select with a number in ms to wait. (Using zero will chew a lot
            // of CPU unless something else in the loop waits.)
            // channelSelector.select(0);
            channelSelector.select(0);

            // Token representing the registration of a SelectableChannel with a Selector
            Set<SelectionKey> myKeys = channelSelector.selectedKeys();
            Iterator<SelectionKey> keyIterator = myKeys.iterator();

            while (keyIterator.hasNext()) {
                SelectionKey myKey = keyIterator.next();

                // Tests whether this key's channel is ready to accept a new socket connection
                if (myKey.isAcceptable()) {
                    SocketChannel myClient = myServerSocketChannel.accept();

                    // Adjusts this channel's blocking mode to false
                    myClient.configureBlocking(false);

                    // Operation-set bit for read operations
                    myClient.register(channelSelector, SelectionKey.OP_READ);
                    System.out.println("Connection Accepted: " + myClient.getLocalAddress());

                    // Tests whether this key's channel is ready for reading
                } else if (myKey.isReadable()) {

                    SocketChannel myClient = (SocketChannel) myKey.channel();
                    ByteBuffer myBuffer = ByteBuffer.allocate(65536);
                    int bytesRead = myClient.read(myBuffer);
                    String result = new String(myBuffer.array());
                    result = result.substring(0, bytesRead);
                    if (result.length() > 0) {
                        fullMessage = fullMessage + result;
                        chunks += 1;
                        System.out.println("Message received " + result.length() + " bytes: \"" + result + "\"");
                    }

                    if (result.endsWith("\n")) {
                        myClient.close();
                        done = true;
                        System.out.println("It's time to close connection as we got a \\n");
                        endTime = System.currentTimeMillis();
                    }
                }
                keyIterator.remove();
            }
        }
        myServerSocketChannel.close();
        channelSelector.close();
        long totalTime = endTime - startTime;
        System.out.println("Done receiving " + fullMessage.length() + " in " + chunks + " chunks over " + totalTime + " ms.");
    }

    public static void main(String[] args) throws Exception {
        while(true)
            handleConnection();
    }
}