FileSender.java

// Author: A0114171W

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketTimeoutException;

class FileSender {

    String srcFileName, hostname, destFileName;
    int portNo;
    PacketHandler handler;

    public static void main(String[] args) {

        // check if the number of command line argument is 3
        if (args.length != 3) {
            System.out.println("Usage: java FileSender <path/filename> "
                    + "<rcvPort> <rcvFileName>");
            System.exit(1);
        }

        FileSender sender = new FileSender(args[0], "localhost", args[1], args[2]);

        try {
            sender.send();
            System.out.println(args[0] + " is successfully sent as " + args[2]);
        } catch (IOException | InterruptedException e) {
            e.printStackTrace();
            System.exit(1);
        }
    }

    public FileSender(String fileToOpen, String host, String port,
            String rcvFileName) {
        srcFileName = fileToOpen;
        hostname = host;
        portNo = Integer.parseInt(port);
        destFileName = rcvFileName;
        handler = new PacketHandler();
    }

    void send() throws IOException, InterruptedException {
        InetAddress rcvAddress = InetAddress.getByName(hostname);
        DatagramSocket socket = new DatagramSocket();
        socket.setSoTimeout(100);

        byte[] dataBuffer = new byte[PacketHandler.MAX_PAYLOAD_LENGTH];

        FileInputStream fis = new FileInputStream(srcFileName);
        BufferedInputStream bis = new BufferedInputStream(fis);

        int seqNo = setupConnection(rcvAddress, socket, destFileName);
        int bytesRead;

        while ((bytesRead = bis.read(dataBuffer)) > 0) {
            byte[] outBuffer =
                    handler.createOutgoingPacket(dataBuffer, bytesRead, seqNo);
            DatagramPacket pktOut =
                    new DatagramPacket(outBuffer, outBuffer.length, rcvAddress, portNo);

            byte[] inBuffer = new byte[PacketHandler.MAX_PACKET_SIZE];
            DatagramPacket pktIn = new DatagramPacket(inBuffer, inBuffer.length);

            seqNo += bytesRead;
            sendUntilReplied(socket, pktOut, pktIn, seqNo);
        }
        closeConnection(rcvAddress, socket, seqNo);
        socket.close();
        bis.close();
    }

    private void closeConnection(InetAddress rcvAddress, DatagramSocket socket,
            int seqNo) throws IOException {
        byte[] outBuffer =
                handler.createFinPacket(seqNo);
        DatagramPacket pktOut =
                new DatagramPacket(outBuffer, outBuffer.length, rcvAddress, portNo);

        byte[] inBuffer = new byte[PacketHandler.MAX_PACKET_SIZE];
        DatagramPacket pktIn = new DatagramPacket(inBuffer, inBuffer.length);

        sendUntilReplied(socket, pktOut, pktIn, seqNo);
    }

    private int setupConnection(InetAddress rcvAddress, DatagramSocket socket,
            String fileName) throws IOException {
        byte[] data = fileName.getBytes();

        int seqNo = 0;
        byte[] outBuffer =
                handler.createSynPacket(data, data.length, seqNo);
        DatagramPacket pktOut =
                new DatagramPacket(outBuffer, outBuffer.length, rcvAddress, portNo);

        byte[] inBuffer = new byte[PacketHandler.MAX_PACKET_SIZE];
        DatagramPacket pktIn = new DatagramPacket(inBuffer, inBuffer.length);

        seqNo += data.length;
        sendUntilReplied(socket, pktOut, pktIn, seqNo);

        return seqNo;
    }

    /**
     * @param socket
     * @param pktOut
     * @param pktIn
     * @param seqNo
     * @throws IOException
     */
    private void sendUntilReplied(DatagramSocket socket, DatagramPacket pktOut,
            DatagramPacket pktIn, int seqNo) throws IOException {
        do {
            socket.send(pktOut);
            try {
                socket.receive(pktIn);
            } catch (SocketTimeoutException e) {
                continue;
            }
        } while (handler.isCorruptedReply(pktIn.getData(), seqNo));
    }
}