I'm working on some code to interact with a server and send a file in 1000 byte chunks. I want to use setSoTimeout to resend a packet after 5 seconds if I have not received an ACK from the server by then. I have searched for the answer to this but to no avail. Here are some links i checked out and attempted:
What is the functionality of setSoTimeout and how it works?
how to use socket.setSoTimeout()?
setSotimeout on a datagram socket
I am under the impression that when the timer is going you are continuously waiting for the ACK. Is this the case? I am never receiving an ACK from the server, although I was at one point before.
import java.net.*;
import java.io.*;
import java.util.*;
public class FTPClient {
Socket tcpSocket;
DatagramSocket udpSocket;
DataInputStream dataIn;
DataOutputStream dataOut;
BufferedReader br;
String fileName;
int time;
int portNum;
/**
* Constructor to initialize the program
*
* @param serverName server name
* @param server_port server port
* @param file_name name of file to transfer
* @param timeout Time out value (in milli-seconds).
*/
public FTPClient(String server_name, int server_port, String file_name, int timeout) {
System.out.println("Server Name: " + server_name + " Server Port: " + server_port
+ " File Name: " + file_name + " Timeout: " + timeout);
fileName = file_name;
time = timeout;
portNum = server_port;
try {
Socket tcpSocket = new Socket(server_name, server_port);
dataIn = new DataInputStream(tcpSocket.getInputStream());
dataOut = new DataOutputStream(tcpSocket.getOutputStream());
br = new BufferedReader(new InputStreamReader(System.in));
}
catch (Exception ex) {
System.out.println("Exception in FTPClient initialization: " + ex);
}
}
/**
*Send file content as Segments
*
*/
public void send() {
try {
File f = new File(fileName);
if (!f.exists()) {
System.out.println("File does not exist...");
return;
}
System.out.println("Sending filename (" + fileName + ") to server.");
dataOut.writeUTF(fileName);
byte msgFromServer = dataIn.readByte();
if (msgFromServer == 0) {
System.out.println("Server ready to receive file");
}
// Create a UDP socket to send the file to the server
DatagramSocket udpSocket = new DatagramSocket();
InetAddress IPAddress = InetAddress.getByName("localhost");
FileInputStream fileIn = new FileInputStream(f);
int seqNum = 0;
int i = 0;
Boolean received = false;;
byte[] chunks = new byte[1000];
int rc = fileIn.read(chunks);
while(rc != -1)
{
System.out.println("Iteration #: " + i);
System.out.println(rc);
// rc should contain the number of bytes read in this operation.
//if (rc < 1000) {
//System.out.println("Bytes read less than 1000");
//System.out.println("Sequence Number: " + seqNum);
//System.out.println("Packet too small to send");
//}
System.out.println("Bytes read greater than 1000");
System.out.println("Sequence Number: " + seqNum);
while (received == false) {
System.out.println("You are looping and sending again");
transferPacket(seqNum, IPAddress, chunks);
received = getResponse();
}
rc = fileIn.read(chunks);
if (seqNum == 1) {
seqNum = 0;
}
else {
seqNum = 1;
}
i++;
}
}
catch (Exception e) {
System.out.println("Error: " + e);
}
}
public Boolean getResponse() {
try {
DatagramSocket udpSocket = new DatagramSocket();
System.out.println("You are in getResponse()");
byte[] receiveData = new byte[1000];
udpSocket.setSoTimeout(time); // set timer
while (true) {
try {
System.out.println("You are receiving a packet");
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
udpSocket.receive(receivePacket);
Segment unwrap = new Segment(receivePacket);
int num = unwrap.getSeqNum();
System.out.println("Received ACK with Sequence Number: " + num);
return true;
}
catch (SocketTimeoutException t) {
System.out.println("Timeout: return false to send()");
return false;
}
}
}
catch (Exception e) {
System.out.println("You don't wanna be here");
return false;
}
}
public void transferPacket(int seqNum, InetAddress IPAddress, byte[] chunks) {
try {
DatagramSocket udpSocket = new DatagramSocket();
byte[] sendData = new byte[1000];
Segment s = new Segment(seqNum, chunks);
sendData = s.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, portNum);
udpSocket.send(sendPacket);
System.out.println("Sent Packet with sequence number " + seqNum);
}
catch (Exception e) {
System.out.println("Exception in transferPacket: " + e);
}
}
/**
* A simple test driver
*
*/
public static void main(String[] args) {
String server = "localhost";
String file_name = "";
int server_port = 8888;
int timeout = 5000; // milli-seconds (this value should not be changed)
// check for command line arguments
if (args.length == 3) {
// either provide 3 parameters
server = args[0];
server_port = Integer.parseInt(args[1]);
file_name = args[2];
}
else {
System.out.println("Wrong number of arguments, try again.");
System.out.println("Usage: java FTPClient server port file");
System.exit(0);
}
FTPClient ftp = new FTPClient(server, server_port, file_name, timeout);
System.out.printf("Sending file \'%s\' to server...\n", file_name);
try {
ftp.send();
}
catch (Exception e) {
System.out.println("Exception: " + e);
}
System.out.println("File transfer completed.");
}
}
