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UDP file send data loss

I have the following codes. I have text file having about 500 kilobytes and I am sending this from client to server this way. Each line in the text file containt 64 letters so 64 bytes. After transfer completed, transferred file is about 150 kbs while my original file is about 500 kbs. Is it okey to send each line by converting to byte first? Also, line order changes in transferred file.
Client
private static DatagramSocket socket;
private static InetAddress address;
private static byte[] buf = new byte[64];
static Scanner file;
public static void main(String[] args) throws IOException{
socket = new DatagramSocket();
address = InetAddress.getByName("localhost");
file = new Scanner(new File("sentfile.txt"));
DatagramPacket packet;
while (file.hasNext()) {
String line = file.nextLine();
if (!line.isEmpty()) {
buf = line.getBytes();
packet = new DatagramPacket(buf, buf.length, address, 1100);
socket.send(packet);
}
}
file.close();
socket.close();
}
Server
private static DatagramSocket udpSocket;
private static byte[] buffer = new byte[64];
private static boolean running;
static PrintWriter writer;
public static void main(String[] args) throws IOException {
udpSocket = new DatagramSocket(1100);
running = true;
writer = new PrintWriter("receivedfile.txt");
DatagramPacket packet;
while(running) {
packet = new DatagramPacket(buffer, buffer.length);
udpSocket.receive(packet);
InetAddress address = packet.getAddress();
int port = packet.getPort();
packet = new DatagramPacket(buffer, buffer.length, address, port);
String received = new String(packet.getData(), 0, packet.getLength());
writer.write(received);
writer.write(System.getProperty("line.separator"));
if (received.equals("end")) {
running = false;
continue;
}
}
writer.close();
udpSocket.close();
}
I know there can be packet loss in udp but 3/2 is lost so I found it too much and wonder if it is because of my code not the nature of udp. Also udp code works slower than udp. Is there a such thing "TCP is faster for small sized data transfer"?

send numbers in UDP socket in java

I am trying to send random numbers inside a UDP socket using this code below but the command sendData = number.getBytes(); is not working. Is it because I have to replace getBytes with something else?
public class UDPServer {
public void run() throws IOException {
DatagramSocket serverSocket = new DatagramSocket(5555);
byte[] receiveData = new byte[1024];
byte[] sendData = new byte[1024];
while (true) {
DatagramPacket receivePacket =
new DatagramPacket(receiveData,
receiveData.length);
serverSocket.receive(receivePacket);
String sentence = new String(receivePacket.getData());
InetAddress IPAddress = receivePacket.getAddress();
int port = receivePacket.getPort();
Random dice = new Random();
int number;
for (int counter = 1; counter <= 10; counter++) {
number = dice.nextInt(6);
}
sendData = number.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData,
sendData.length, IPAddress, port);
serverSocket.send(sendPacket);
}

I take it you want to write the bytes of your ints in network byte order. Good. Java has a class for it: ByteBuffer.
Sample code, modify for your needs:
final ByteBuffer buf = ByteBuffer.allocate(8); // for 2 ints, an int is 4 bytes long
buf.putInt(4);
buf.putInt(3);
buf.rewind();
final DatagramPacket packet
= new DatagramPacket(buf.array(), buf.limit(), addr, port);
ByteBuffer does big endian by default, which is the network byte order. See its .order() method.

Inexperienced java user requesting advice with classes

I have created a class which sends a single datagram packet, which is successfully received by another program.
import java.net.*;
public class UDPServer {
public static void main(final String args[]) throws Exception {
final String sendID = "level1";
final int val = 2;
final DatagramSocket serverSocket = new DatagramSocket(7474);
byte[] sendData = new byte[1024];
final InetAddress IPAddress = InetAddress.getLocalHost();
final String sentence = sendID + new String(" ")
+ new Integer(val).toString();
final String capitalizedSentence = sentence.toUpperCase();
sendData = capitalizedSentence.getBytes();
final DatagramPacket sendPacket = new DatagramPacket(sendData,
sendData.length, IPAddress, 7470);
serverSocket.send(sendPacket);
}
}
My question is how could I run this code from another, passing on variables for sendID and val. This is eventually going to be sending information from a game to audio programming software, to create algorithmic scores.
Apologies if the code is wrong/badly formatted, I'm not a programmer by trade!
Thanks.

Juste create a method Send with two parameters
public class UDPServer {
public void send(final String sendID, final int val) throws Exception {
final DatagramSocket serverSocket = new DatagramSocket(7474);
byte[] sendData = new byte[1024];
final InetAddress IPAddress = InetAddress.getLocalHost();
final String sentence = sendID + new String(" ")
+ new Integer(val).toString();
final String capitalizedSentence = sentence.toUpperCase();
sendData = capitalizedSentence.getBytes();
final DatagramPacket sendPacket = new DatagramPacket(sendData,
sendData.length, IPAddress, 7470);
serverSocket.send(sendPacket);
}
}
And now from another class
UDPServer server = new UDPServer();
server.send("level1", 2);
Few comments on your code:
Avoid using variable with the first letter in capital (i.e. IPAddress). Usually classes start with a capital letter, not variables.
You can simplify :
byte[] sendData = new byte[1024];
sendData = capitalizedSentence.getBytes();
by
byte[] sendData = capitalizedSentence.getBytes();
and
final String sentence = sendID + new String(" ")
+ new Integer(val).toString();
by
final String sentence = String.format("%s %d", sendID, val);

UDP threading infinite loop in Java

I've written two programs. Now each program uses threading to send and receive packets at the same time.
Whenever I send packets from the server to the client, the message at the client ends gets received in an infinite loop. I.e; I've added a print statement that prints the message sent and this goes forever in an infinite loop. I want to make it so that it receives the message, and then be able to write back to the server and exit whenever the user wants to.
I've tried using socket.close(), but this makes it so that the client receives the message and I can only write back to the server once. After I send it, I can't send anymore. I want to make it so that I can write back more than once.
Can anyone please point me in the right direction?
My code is as follows;
public class UDPThreadClient extends Thread {
public static int port1;
//Create threaded server
UDPThreadClient (int port1) {
System.out.println ("Starting threaded client");
start();
}
public void run() {
int port = port1;
try {
DatagramSocket serverSocket = new DatagramSocket(port1);
byte[] receiveData = new byte[1024];
byte[] sendData = new byte[1024];
while (true) {
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
String sentence = new String( receivePacket.getData());
SocketAddress address = receivePacket.getSocketAddress();
System.out.println("RECEIVED from " + address + " : " + sentence);
InetAddress IPAddress = receivePacket.getAddress();
//int port = receivePacket.getPort();
String capitalizedSentence = sentence.toUpperCase();
sendData = capitalizedSentence.getBytes();
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress, port);
serverSocket.send(sendPacket);
//serverSocket.close();
}
} catch (IOException e) {
System.out.println (e.getMessage());
}
}
//Create client
public static void main(String[] args) {
int port = Integer.parseInt(args[0]);
port1 = Integer.parseInt(args[1]);
new UDPThreadClient (port1);
try {
BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
DatagramSocket clientSocket = new DatagramSocket();
InetAddress IPAddress = InetAddress.getByName("localhost");
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
String sentence = inFromUser.readLine();
sendData = sentence.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port);
clientSocket.send(sendPacket);
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(receivePacket);
String modifiedSentence = new String(receivePacket.getData());
System.out.println("FROM SERVER:" + modifiedSentence);
//clientSocket.close();
} catch (IOException e) {
System.out.println (e.getMessage());
}
}
}
and
public class UDPThreadServer extends Thread {
public static int port1;
//Create threaded client
UDPThreadServer () {
System.out.println ("Starting threaded server");
start();
}
public void run() {
try {
DatagramSocket clientSocket = new DatagramSocket();
BufferedReader inFromUser = new BufferedReader (new InputStreamReader(System.in));
Scanner in = new Scanner (inFromUser);
InetAddress IPAddress = InetAddress.getByName("localhost");
byte[] sendData = new byte [1024];
byte[] receiveData = new byte [1024];
while (in.hasNextLine()) {
String sentence = in.nextLine();
//inFromUser.readLine();
sendData = sentence.getBytes();
DatagramPacket sendPacket = new DatagramPacket (sendData, sendData.length, IPAddress, port1);
clientSocket.send(sendPacket);
DatagramPacket receivePacket = new DatagramPacket (receiveData, receiveData.length);
clientSocket.receive (receivePacket);
String modSentence = new String (receivePacket.getData());
System.out.println ("FROM SERVER: " + modSentence);
}
//clientSocket.close();
} catch (IOException e) {
System.out.println (e.getMessage());
}
}
//Create server
public static void main(String[] args) {
int port = Integer.parseInt(args[0]);
port1 = Integer.parseInt(args[1]);
new UDPThreadServer ();
try {
DatagramSocket serverSocket = new DatagramSocket (port);
byte[] receiveData = new byte[1024];
byte[] sendData = new byte[1024];
while (true) {
DatagramPacket receivePacket = new DatagramPacket (receiveData, receiveData.length);
serverSocket.receive(receivePacket);
String sentence = new String(receivePacket.getData());
SocketAddress address = receivePacket.getSocketAddress();
System.out.println ("Received from " + address + " : " + sentence);
InetAddress IPAddress = receivePacket.getAddress();
String capSentence = sentence.toUpperCase();
sendData = capSentence.getBytes();
DatagramPacket sendPacket = new DatagramPacket (sendData, sendData.length, IPAddress, port);
serverSocket.send(sendPacket);
//serverSocket.close();
}
} catch (IOException e) {
System.out.println (e.getMessage());
}
}
}
Thanks.

Looking at UDPClientServer:
When you create the Datagram packet, you give it the port to send it to, not the port that you are sending it from.
When I ran your code, nothing happened. The server is waiting on port port, while the client sends to port port1. If you instead send to port port (not accessible from the main method, but changing it to a field instead of local method would fix that, then the infinite looping occurs because the server sends a packet to the same port it is listening on. There's your problem. Do you supply the same numbers as the first and second arguments to your program?
From the server, you can use receivePacket.getPort() to get the port where the packet came from.
EDIT:
Your two classes have much repetition, which is probably a source of confusion. One class has a main which starts a client then creates a server type loop tester. The other class sets up a Server then creates a client type tester.
Below is only the class you've named UDPThreadServer with comments showing changes to make the server 'work' with the testing code in the main method. Note that the server should send to a port that it is not listening to. You are also reading port values from command line arguments. I just made up some numbers for the ports and stuck them in as constants.
public class UDPThreadServer extends Thread
{
public static int port1;
UDPThreadServer()
{
//server or client? it's hard to say. you call the socket a clientSocket.
System.out.println("Starting threaded server");
start();
}
public void run()
{
try
{
// Here client(?) is set up with empty constructor.
// It is a mystery what port it will get.
DatagramSocket clientSocket = new DatagramSocket();
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
Scanner in = new Scanner(inFromUser);
InetAddress IPAddress = InetAddress.getByName("localhost");
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
while (in.hasNextLine())
{
String sentence = in.nextLine();
// inFromUser.readLine();
sendData = sentence.getBytes();
// sending to port1? that must be the server.
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress, port1);
clientSocket.send(sendPacket);
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(receivePacket);
String modSentence = new String(receivePacket.getData());
System.out.println("FROM SERVER: " + modSentence);
}
// clientSocket.close();
} catch (IOException e)
{
System.out.println(e.getMessage());
}
}
// Create server
public static void main(String[] args)
{
// int port = Integer.parseInt(args[0]);
int port = 1927; // or whatever
// port1 = Integer.parseInt(args[1]);
port1 = 1928;
new UDPThreadServer();
try
{
// server resides on port1? if client sends to port 1, then this is so.
DatagramSocket serverSocket = new DatagramSocket(port1);
byte[] receiveData = new byte[1024];
byte[] sendData = new byte[1024];
while (true)
{
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
String sentence = new String(receivePacket.getData());
SocketAddress address = receivePacket.getSocketAddress();
System.out.println("Received from " + address + " : " + sentence);
InetAddress IPAddress = receivePacket.getAddress();
String capSentence = sentence.toUpperCase();
sendData = capSentence.getBytes();
// where did you get the info from? Client is set up with an empty constructor, so it is a mystery.
port = receivePacket.getPort();
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress, port);
serverSocket.send(sendPacket);
// serverSocket.close();
}
} catch (IOException e)
{
System.out.println(e.getMessage());
}
}
}

Don't close the socket.
If that doesn't answer your question you need to clarify it.

while(true) is an infinite loop. Do you quit it in any case?

client server udp socket

Hi i have a udp client server code that is not working i ask a general question "Is shane a good kid"both codes have no errors that come up but when i run the code it outputs
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
instead of letting the client greet the server. The flow should be Server initializes and waits for client--client greets server -- server asks the question -- client responds to question-- server tallies the yes no votes and displays weather or not the person is like =.
any advice on how to round the code out would be welcomed
hear is the server code
import java.net.*;
public class VotingServer {
//private static final int yes = 0;
private static int yes2;
public static void main(String[] args, int getrep) throws Exception{
// part 1: initialization
DatagramSocket serverSocket = new DatagramSocket(9876);
byte[] receiveData = new byte[1024];
byte[] sendData = new byte[1024];
InetAddress[] IPAddressList = new InetAddress[5];
int[] portList = new int[5];
// part 2: receive the greeting from clients
for (int i=0; i<1; i++) {
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
String greeting = new String(receivePacket.getData());
System.out.println("From Client: " + greeting);
IPAddressList[i] = receivePacket.getAddress();
portList[i] = receivePacket.getPort();
} // for (i)
// part 3: broadcast the votiong question to all clients
String question = "is shane a good kid 1 for yes 0 no?\n";
for (int i=0; i<5; i++) {
sendData = question.getBytes();
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length);
serverSocket.send(sendPacket);
// part 5: receive the age of client (B)
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
String ageStr = new String(receivePacket.getData());
yes2 = Integer.parseInt(ageStr);
IPAddressList[i] = receivePacket.getAddress();
portList[i] = receivePacket.getPort();
// part 6: compute the price (C)
double count= 0;
double no = 0;
if (yes2 >= 1 ) count = 1;
else
if (yes2 <= 0 ) no = 1;
// part 7: send the price to client
String rep = null;
String countStr = ""+count+"\n";
String noStr = ""+no+"\n";
if (no < count) rep = "Is a good kid";
else
if (no > count) rep = "is a bad kid";
System.out.println(" "+getrep);
sendData = countStr.getBytes();
sendData = noStr.getBytes();
sendData = rep.getBytes();
DatagramPacket sendPacket1 =
new DatagramPacket(sendData, sendData.length);
serverSocket.send(sendPacket1);
} // main()
}} // UDPServer
And here is the client code
import java.io.;
import java.net.;
public class ClientVoting {
public static void main(String[] args) throws Exception {
// part 1: initialization
BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
DatagramSocket clientSocket = new DatagramSocket();
InetAddress IPAddress = InetAddress.getByName("localhost");
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
String sentence = inFromUser.readLine();
sendData = sentence.getBytes();
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket);
// part 2: receive the question from server
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(receivePacket);
String question = new String(receivePacket.getData());
System.out.println("From Server:" + question);
String yes2 = inFromUser.readLine();
sendData = yes2.getBytes();
DatagramPacket sendPacket1 =
new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket1);
// part 4: get the price from server
receivePacket = new DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(receivePacket);
String rep = new String(receivePacket.getData());
System.out.println("the answer is " + rep);
// part 4: close the socket
clientSocket.close();
} // main()
} // class UDPClient
Thanks SPF

I get a NullPointException running your code in the Server-side... There are a few problems in the code itself. The first one is the index of the Array that you attempt to keep the instance of the Clients connection. At this point, you have only one...
for (int i=0; i<1; i++) {
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
String greeting = new String(receivePacket.getData());
System.out.println("From Client: " + greeting);
IPAddressList[i] = receivePacket.getAddress();
portList[i] = receivePacket.getPort();
} // for (i)
However, at this point, your code is prone to NullPointException as you try to iterate over it 5 times...
String question = "is shane a good kid 1 for yes 0 no?\n";
for (int i=0; i<5; i++) {
sendData = question.getBytes();
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length);
serverSocket.send(sendPacket); <<<<---- NPE prone code line...
Here's the result of running the code...
From Client: hello
Exception in thread "main" java.lang.NullPointerException: null buffer || null address
at java.net.PlainDatagramSocketImpl.send(Native Method)
at java.net.DatagramSocket.send(DatagramSocket.java:629)
at com.vasoftware.sf.common.VotingServer.main(VotingServer.java:38)
Looking at this exception, I noticed that since your buffer would not be null, your address is the problem, since you create a new DatagramPacket without both the IP and the Port number of the client connection... You have to pass them to the DatagramPacket instance so that the server knows who is the client trying to communicate... A very simple/basic example of what you are trying to achieve is at http://systembash.com/content/a-simple-java-udp-server-and-udp-client/. Below is my initial fixing of the code... Your answers will still need some work on the buffer, which I will leave it as an exercise...
Here's a fixed code for Server that accepts only 1 client... I will leave the Multi-threaded stuff + the data handler for you as an exercise...
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.Arrays;
public class VotingServer {
//private static final int yes = 0;
private static int yes2;
public static void main(String[] args) throws Exception {
// part 1: initialization
DatagramSocket serverSocket = new DatagramSocket(9876);
byte[] receiveData = new byte[1024];
byte[] sendData = new byte[1024];
InetAddress IPAddressList;
int portList = -1;
// part 2: receive the greeting from clients
System.out.println("Ready to receive connections at port " + serverSocket.getLocalPort());
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
String greeting = new String(receivePacket.getData());
System.out.println("From Client: " + greeting);
IPAddressList = receivePacket.getAddress();
portList= receivePacket.getPort();
// part 3: broadcast the votiong question to all clients
String question = "is shane a good kid 1 for yes 0 no?\n";
sendData = question.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddressList, portList);
serverSocket.send(sendPacket);
// part 5: receive the age of client (B)
receiveData = new byte[1024];
receivePacket = new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
String ageStr = new String(receivePacket.getData());
try {
yes2 = Integer.parseInt(ageStr); //<<<----- WILL NEVER GET THE VALUE... LEAVING IT AS AN EXERCISE....
} catch (NumberFormatException nfe) {
yes2 = 0;
}
receivePacket.getAddress();
receivePacket.getPort();
// part 6: compute the price (C)
double count= 0;
double no = 0;
if (yes2 >= 1 ) count = 1;
else
if (yes2 <= 0 ) no = 1;
// part 7: send the price to client
// ALSO FIXING SOME CODE HERE AS WELL....
String rep = null;
rep = no < count ? "Is a good kid" : "is a bad kid";
rep += " Server Count: " + count;
sendData = rep.getBytes();
DatagramPacket sendPacket1 = new DatagramPacket(sendData, sendData.length, IPAddressList, portList);
serverSocket.send(sendPacket1);
}
}
Here's the client-side:
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
public class ClientVoting {
public static void main(String[] args) throws Exception {
// part 1: initialization
BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
DatagramSocket clientSocket = new DatagramSocket();
InetAddress IPAddress = InetAddress.getByName("localhost");
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
System.out.print("What's the question? ");
String sentence = inFromUser.readLine();
sendData = sentence.getBytes();
System.out.println("Attempting to connect the server at port " + 9876);
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket);
System.out.println("Initial greeting sent... Waiting for response...");
// part 2: receive the question from server
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(receivePacket);
String question = new String(receivePacket.getData());
System.out.println("From Server:" + question);
String yes2 = inFromUser.readLine();
sendData = yes2.getBytes();
DatagramPacket sendPacket1 =
new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket1);
// part 4: get the price from server
receiveData = new byte[1024];
receivePacket = new DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(receivePacket);
String rep = new String(receivePacket.getData());
System.out.println("the answer is " + rep);
// part 4: close the socket
clientSocket.close();
} // main()
}
You MUST execute the server first, as it will listen to the socket open on port 9876. Then, you can connect to the server with the client.
###### Here's the output in the server-side... Just added a few details of what's going on...
Ready to receive connections at port 9876
From Client: Marcello
####### Here's the output of the client:
What's the question? Marcello
Attempting to connect the server at port 9876
Initial greeting sent... Waiting for response...
From Server:is shane a good kid 1 for yes 0 no?
the answer is is a bad kid Server Count: 0.0
As it seems that your requirement is to design a Server that can handle multiple clients and count on the number of votes, I would also recommend you to use a Multi-threaded version of the server by using different Threads to deal with each client in its own thread and update the value of the static counter (an example is a while(true) loop executing a new Runnable with an Executor here http://java-x.blogspot.com/2006/11/java-5-executors-threadpool.html). Think about creating a Runnable instance as described, and placing the server's code in the public void run() {} method implementation... I will leave this as an exercise for you as well...