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Multiple file chunks transfer over socket to multiple clients

I have to transfer chunks of a file to different clients using one server.
When i run the server file and provide the name of the file it successfully makes chunks. when i run the first client for first time it works but when i run it for the client again(by that i mean when i connect as a second client) it fails to transfer chunks to the second client. Complete code of server and client are shown below.
error is for the second client it starts reading the contents of the file as filename and program terminates.
provide a large text file(1MB) file as input to server
Server Code:
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.*;
public class server {
private static final int sPort = 8000; //The server will be listening on this port number
public static String str;
public static int c;
public static void main(String[] args) throws Exception {
System.out.println("The server is running.");
ServerSocket listener = new ServerSocket(sPort);
int clientNum = 1;
System.out.println("Enter the name of the file: ");
Scanner in = new Scanner(System.in);
str = in.nextLine();
String path = System.getProperty("user.dir");
String filepath = path +"/"+ str;
in.close();
try {
c=splitFile(new File(filepath));
} catch (IOException e1) {
e1.printStackTrace();
}
try {
while(true) {
new Handler(listener.accept(),clientNum,c).start();
System.out.println("Client " + clientNum + " is connected!");
clientNum++;
}
} finally {
listener.close();
}
}
/**
* A handler thread class. Handlers are spawned from the listening
* loop and are responsible for dealing with a single client's requests.
*/
private static class Handler extends Thread {
private Socket connection;
private int chunkcount;
private ObjectInputStream in; //stream read from the socket
private ObjectOutputStream out; //stream write to the socket
private int no; //The index number of the client
public Handler(Socket connection, int no,int c) {
this.connection = connection;
this.no = no;
this.chunkcount=c;
}
public void run() {
try{
//initialize Input and Output streams
out = new ObjectOutputStream(connection.getOutputStream());
out.flush();
in = new ObjectInputStream(connection.getInputStream());
try{
String path = System.getProperty("user.dir");
path=path+"/"+"chunks"+ "/";
System.out.println(path);
System.out.println("Total chunks: "+chunkcount);
int i=no;
int j=i;
int k=0;
OutputStream op=connection.getOutputStream();
DataOutputStream d = new DataOutputStream(op);
d.writeInt(no);
d.flush();
System.out.println("value of j or clientnum: "+j);
while(j<chunkcount)
{
k++;
j=j+5;
}
System.out.println(k);
d.writeInt(k);
d.flush();
//d.close();
while(i<chunkcount)
{
String pathname= path+Integer.toString(i)+str;
System.out.println(i+str);
sendFile(connection,pathname);
i=i+5;
}
}
catch(Exception e){
e.printStackTrace();
}
}
catch(IOException ioException){
System.out.println("Disconnect with Client " + no);
}
finally{
//Close connections
try{
in.close();
out.close();
connection.close();
}
catch(IOException ioException){
System.out.println("Disconnect with Client " + no);
}
}
}
}
public static int splitFile(File f) throws IOException {
int partCounter = 1;//I like to name parts from 001, 002, 003, ...
//you can change it to 0 if you want 000, 001, ...
int sizeOfFiles = 102400;// 1MB
byte[] buffer = new byte[sizeOfFiles];
try (BufferedInputStream bis = new BufferedInputStream(
new FileInputStream(f))) {//try-with-resources to ensure closing stream
String name = f.getName();
String path = f.getParent();
long sizefile = f.getTotalSpace();
String newpath = path + "/" + "chunks";
File dir = new File(newpath);
dir.mkdir();
int tmp = 0;
while ((tmp = bis.read(buffer)) > 0) {
//write each chunk of data into separate file with different number in name
File newFile = new File(dir, String.format("%d", partCounter++) + name );
//System.out.println(f.getParent());
try (FileOutputStream out = new FileOutputStream(newFile)) {
out.write(buffer, 0, tmp);//tmp is chunk size
}
}
System.out.println("File details are : "+name+" "+sizefile);
System.out.println("Number of chunks: "+ (partCounter-1));
}
return (partCounter-1);
}
public static void sendFile(Socket conn,String fileName) throws IOException
{
File myFile = new File(fileName);
byte[] mybytearray = new byte[(int) myFile.length()];
FileInputStream fis = new FileInputStream(myFile);
BufferedInputStream bis = new BufferedInputStream(fis);
DataInputStream dis = new DataInputStream(bis);
dis.readFully(mybytearray, 0, mybytearray.length);
OutputStream os = conn.getOutputStream();
DataOutputStream dos = new DataOutputStream(os);
dos.writeUTF(myFile.getName());
dos.writeLong(mybytearray.length);
dos.write(mybytearray, 0, mybytearray.length);
dos.flush();
dis.close();
}
}
client code:
import java.net.*;
import java.io.*;
public class Client {
Socket requestSocket; //socket connect to the server
ObjectOutputStream out; //stream write to the socket
ObjectInputStream in; //stream read from the socket
public Client() {}
void run()
{
try{
//create a socket to connect to the server
requestSocket = new Socket("localhost", 8000);
System.out.println("Connected to localhost in port 8000");
//initialize inputStream and outputStream
out = new ObjectOutputStream(requestSocket.getOutputStream());
out.flush();
in = new ObjectInputStream(requestSocket.getInputStream());
System.out.println("Ready to receive files ( Enter QUIT to end):");
BufferedInputStream in1 = new BufferedInputStream(requestSocket.getInputStream());
DataInputStream d = new DataInputStream(in1);
int clientnum=d.readInt();
String path = System.getProperty("user.dir");
String oppath = path + "/" + "Client" + clientnum;
File dir = new File(oppath);
dir.mkdir();
int numchunk=d.readInt();
System.out.println(numchunk);
int jakarta=1;
while(jakarta<=numchunk ){
jakarta++;
String newpath=oppath+"/";
File f = new File(newpath);
f.createNewFile();
receiveFile(requestSocket,newpath);
System.out.println("File Received");
}
}
catch (ConnectException e) {
System.err.println("Connection refused. You need to initiate a server first.");
}
catch(UnknownHostException unknownHost){
System.err.println("You are trying to connect to an unknown host!");
}
catch(IOException ioException){
ioException.printStackTrace();
}
finally{
//Close connections
try{
in.close();
out.close();
requestSocket.close();
}
catch(IOException ioException){
ioException.printStackTrace();
}
}
}
//send a message to the output stream
public static void receiveFile(Socket s1,String oppath) throws IOException
{
String fileName;
try {
int bytesRead;
InputStream in = s1.getInputStream();
DataInputStream clientData = new DataInputStream(in);
fileName = clientData.readUTF();
OutputStream output = new FileOutputStream(oppath+fileName);
long size = clientData.readLong();
byte[] buffer = new byte[1024];
while (size > 0
&& (bytesRead = clientData.read(buffer, 0,
(int) Math.min(buffer.length, size))) != -1) {
output.write(buffer, 0, bytesRead);
size -= bytesRead;
}
output.flush();
output.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
//main method
public static void main(String args[])
{
Client client = new Client();
client.run();
}
}

Websocket server to initialise a connection to another websocket server

Is there a way to get a websocket server to connect to another websocket server? I wrote this snippet in Java but it doesn't work. I don't get any errors or exceptions, it just waits forever to connect.
#OnMessage
public void message(Session session, String msg){
String URL = "ws://wildfly2-ciri.rhcloud.com:8000/echo";
try {
System.out.println("**1 Got new message: " + msg);
String forward = "This is WildFly 1: " + msg;
System.out.println("**1 Init new session");
Session newSession = session.getContainer().connectToServer(Client.class, URI.create(URL));
System.out.println("**1 Sending to wildfly2");
newSession.getBasicRemote().sendText(forward);
} catch (Exception e) {
e.printStackTrace();
}
}
Basically, I want this server to initialize a new websocket connection to another server at another address. However, the program stops when it tries to make a new connection. Is there a flaw in my thinking or is this kind of connection impossible?

You may find this useful. This is one of my older socket programs which I used to communicate between client and server. I have attached both of client and code for the program which would send XML files. You will however, need to edit a few things in order to get her workin' for you. Play this with file and get a feel for sockets and apply it to your program. Happy Learnings my friend!
public static void main(String[] args) throws IOException {
Socket socket = null;
String host = "127.0.0.1";
socket = new Socket(host, 4444);
File file = new File("C:\\testXML.xml");
// Get the size of the file
long length = file.length();
if (length > Integer.MAX_VALUE) {
System.out.println("File is too large.");
}
byte[] bytes = new byte[(int) length];
FileInputStream fis = new FileInputStream(file);
BufferedInputStream bis = new BufferedInputStream(fis);
BufferedOutputStream out = new BufferedOutputStream(socket.getOutputStream());
int count;
while ((count = bis.read(bytes)) > 0) {
out.write(bytes, 0, count);
}
out.flush();
out.close();
fis.close();
bis.close();
socket.close();
}
}
public class Server {
/**
* #param args the command line arguments
*/
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(4444);
} catch (IOException ex) {
System.out.println("Can't setup server on this port number. ");
}
Socket socket = null;
InputStream is = null;
FileOutputStream fos = null;
BufferedOutputStream bos = null;
int bufferSize = 0;
try {
socket = serverSocket.accept();
} catch (IOException ex) {
System.out.println("Can't accept client connection. ");
}
try {
is = socket.getInputStream();
bufferSize = socket.getReceiveBufferSize();
System.out.println("Buffer size: " + bufferSize);
} catch (IOException ex) {
System.out.println("Can't get socket input stream. ");
}
try {
fos = new FileOutputStream("C:\\xxxXXXXxxx.txt");
bos = new BufferedOutputStream(fos);
} catch (FileNotFoundException ex) {
System.out.println("File not found. ");
}
byte[] bytes = new byte[bufferSize];
int count;
while ((count = is.read(bytes)) > 0) {
bos.write(bytes, 0, count);
}
bos.flush();
bos.close();
is.close();
socket.close();
serverSocket.close();
}
}

Null pointer exception occurs while trying to read repeatedly from an InputStream

The code works fine when I close the client just after sending one instruction. But when I want a client and server connection to persist, so that the client can send multiple instructions to the server one after another, I get a Null pointer exception at the server and the message java.net.SocketException: Socket is closed at the client. This happens after the client sends a file to the server and the server successfully receives it. Need help. The error occurs at the Connection class code line switch(clientMsg). It seems to me that for some reason the BufferedReader in goes null, but I might be mistaken about that. The code is as follows. Thanks.
Server
public class server {
private static ServerSocket serverSocket;
private static Socket socket = null;
public static void print(Object s) {
System.out.println(s);
}
#SuppressWarnings("resource")
public static void main (String args[]) throws IOException {
System.out.print("Specify listening port: ");
Scanner _a = new Scanner(System.in);
int a = _a.nextInt();
try{
serverSocket = new ServerSocket(a);
}
catch(IOException e) {
System.out.println(e);
}
while (true) {
try {
socket = serverSocket.accept();
print("Connected to " + socket);
Thread client = new Thread(new Connection(socket));
client.start();
}
catch (IOException e) {
print(e);
}
}
}
}
Connection
public class Connection implements Runnable {
public static void print(Object s) {
System.out.println(s);
}
private Socket socket;
private BufferedReader in = null;
public Connection(Socket client) {
this.socket = client;
}
#Override
public void run(){
try {
in = new BufferedReader(new InputStreamReader(
socket.getInputStream()));
String clientMsg;
while (true) {
clientMsg = in.readLine();
switch (clientMsg) {
case "1":
receiveFile(); //method code not included
break;
default:
print("Command not recognized");
break;
}
//in.close();
}
}//try run()
catch (IOException e) {
print(e);
}
}
Client
public class client {
private static Socket connectToServer;
private static String fileName;
private static BufferedReader keybrdIn;
private static PrintStream msgToServer;
public static void println(Object e) {
System.out.println(e);
}
public static void print(Object e) {
System.out.print(e);
}
public static void main(String args[]) throws IOException{
try{
print("Enter IP: ");
String ip = new Scanner(System.in).nextLine();
print("Enter port: ");
int port = new Scanner(System.in).nextInt();
connectToServer = new Socket(ip, port);
keybrdIn = new BufferedReader(new InputStreamReader(System.in));
}catch(IOException e) {
println(e);
}
msgToServer = new PrintStream(connectToServer.getOutputStream());
while (true) {
try {
switch(Integer.parseInt(action())) { //action() method code not included
case 1:
msgToServer.println("1");
sendFile();
break;
default:
println("Invalid input");
break;
}
}catch (IOException e) {
println(e);
}
}
}
sendFile()
public static void sendFile() throws IOException {
print("Enter file name: ");
fileName = keybrdIn.readLine();
File file = new File(fileName);
byte[] bytearray = new byte[8192];
FileInputStream fis = new FileInputStream(file);
BufferedInputStream bis = new BufferedInputStream(fis);
DataInputStream dis = new DataInputStream(bis);
OutputStream os = connectToServer.getOutputStream();
DataOutputStream dos = new DataOutputStream(os);
dos.writeUTF(file.getName());
int count;
while ((count = dis.read(bytearray)) > 0){
dos.write(bytearray, 0, count);
}
dis.close();
dos.flush();
dos.close();
}
receiveFile()
public void receiveFile() {
try {
int count;
DataInputStream clientFileStream = new DataInputStream(socket.getInputStream());
String fileName = clientFileStream.readUTF();
OutputStream fileOutput = new FileOutputStream("_" + fileName);
byte[] mybytearray = new byte[8192];
BufferedOutputStream bos = new BufferedOutputStream(fileOutput);
System.out.println("Downloading " + fileName + " ...");
//outToClient().writeBytes("Uploading. Please wait...\n");
while ((count = clientFileStream.read(mybytearray)) > 0){
bos.write(mybytearray, 0, count);
}
fileOutput.close();
bos.close();
clientFileStream.close();
}
catch (IOException e) {
print(e);
}
}

In sendFile(), you close the data output stream which closes your underlying connection's output stream.
According to the documentation of Socket.getOutputStream():
"Closing the returned OutputStream will close the associated socket".

Since you already closed stream, it will also close socket as well as Eyal mentioned. However, at the moment you close the stream, server side will aware of that and return -1 for read() results.
So, even if you didn't specify file length at beginning, this will generally works well.
However, since you already closed stream, you can't reuse it no matter what. To fix this issue, probably you need to change your Client class so that Client should create socket connection, send files, close socket. That's one lifecycle of opened client socket.
Or maybe in while loop of Client class, 1) take ip, port, and filename to send 2) Create new Thread and provide those information so let thread open connection, send file, close connection 3) and in the meantime, client while() can keep take next ip, port, and filename to send from the user. By doing this, you don't need to make client program wait until file transfer to be completed.

Regarding the NPE in the server, readLine() returns null at end of stream. You are ignoring it. You should be testing for it immediately after the call, and if null close the socket and exit the read loop.

File transfer Server to client - java

I am trying to write the server client file transfer program in java.
Role of Server:-
a) Serve a file to a client (one).
b) Server will send file 1 byte at a time.
c) Should be able to send the file more than once.
Role of Client:-
a) Client downloads a file
b) Client should buffer the file before writing to disk( <= 100kb) I.e. buffer 100KB and write to disk then repeat this till 1MB
I wrote the code to transfer the file from Server to Client but there seem to have some issues with the program. Server starts sending the data but its lost in the transaction. Also the content of file to be transferred is erased. As I couldn't see any specific error on console so I couldn't figure out the bug. If anyone guide me whether this approach is correct or if not, please suggest proper changes.
*Server*
public class Server {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
Socket socket = null;
InputStream inputStream = null;
FileOutputStream fileOutputStream = null;
BufferedOutputStream bufferedOutputStream = null;
int sizeBuffer = 0;
try{
try {
serverSocket = new ServerSocket(55555);
} catch (IOException ex) {
System.out.println("Error: Unable to Connect to Server ");
}
System.out.println("Created Socket");
try {
socket = serverSocket.accept();
} catch (IOException ex) {
System.out.println("Error: Unable to connect to client ");
}
System.out.println("Accepted Client Connection ");
try {
inputStream = socket.getInputStream();
sizeBuffer = socket.getReceiveBufferSize();
System.out.println("Size of Buffer " + sizeBuffer);
} catch (IOException ex) {
System.out.println("Error: unable to ger socket input stream ");
}
try {
fileOutputStream = new FileOutputStream("D:/ServerFile.txt");
bufferedOutputStream = new BufferedOutputStream(fileOutputStream);
} catch (FileNotFoundException ex) {
System.out.println("File not found. ");
}
byte[] bytes = new byte[sizeBuffer];
int count;
while ((count = inputStream.read(bytes)) > 0) {
bufferedOutputStream.write(bytes, 0, count);
}
System.out.println("Done");
}// end of first try
finally{
bufferedOutputStream.flush();
bufferedOutputStream.close();
inputStream.close();
socket.close();
serverSocket.close();
}
}
}
And here is client side code !
*Client*
public class Client {
public static void main(String[] args) throws IOException {
FileInputStream fileInputStream = null;
BufferedInputStream bufferedInputStream = null;
BufferedOutputStream bufferedOuptputStream = null;
Socket socket = null;
int count;
try{
try {
socket = new Socket("127.0.0.1", 55555);
} catch (IOException ex) {
System.out.println("Error: Unable to create Socket ");
}
File file = new File("D:/ClientFile.txt");
long fileLength = file.length();
System.out.println(fileLength);
if ( Integer.MAX_VALUE < fileLength ) {
System.out.println("Error: Exceeded the size of transfer");
}
byte[] bytes = new byte[(int) fileLength];
try{
fileInputStream = new FileInputStream(file);
}catch (IOException ex){
System.out.println("Error: Unable to open fileInputStream");
}
bufferedInputStream = new BufferedInputStream(fileInputStream);
bufferedOuptputStream = new BufferedOutputStream(socket.getOutputStream());
while ((count = bufferedInputStream.read(bytes)) > 0) {
bufferedOuptputStream.write(bytes, 0, count);
}
}
finally{
bufferedOuptputStream.flush();
bufferedOuptputStream.close();
fileInputStream.close();
bufferedInputStream.close();
socket.close();
}
}
}

Implementation of a simple file transfer client server

Hi I have the following code to the client - server through the thread, I have a errors,
Can't setup server on this port number.
Can't setup server on this port number.
but why?
class client:
import java.io.*;
import java.net.Socket;
// create class client
public class Client extends Thread {
Socket socket = null;
Socket socket1 = null;
// create send method
public void sendFile() throws IOException {
String host = "127.0.0.1";
String host1 = "127.0.0.2";
socket = new Socket(host, 4444);
socket1 = new Socket(host1, 444);
File file = new File("/home/reza/Desktop/link help");
File file1 = new File("/home/reza/Desktop/hi");
long length = file.length();
long length1 = file1.length();
byte[] bytes = new byte[(int) length];
byte[] bytes1 = new byte[(int) length1];
FileInputStream fis = new FileInputStream(file);
FileInputStream fis1 = new FileInputStream(file1);
BufferedInputStream bis = new BufferedInputStream(fis);
BufferedOutputStream out = new BufferedOutputStream(socket.getOutputStream());
BufferedInputStream bis1 = new BufferedInputStream(fis1);
BufferedOutputStream out1 = new BufferedOutputStream(socket1.getOutputStream());
int count;
int count1;
while ((count = bis.read(bytes)) > 0) {
out.write(bytes, 0, count);
}
while ((count1 = bis1.read(bytes1)) > 0) {
out1.write(bytes1, 0, count1);
}
Thread t = new Thread(new Runnable() {
public void run()
{
while(socket.isConnected())
{
Wait2();
try {
sendFile();
} catch (IOException e) {
e.printStackTrace();
}
}
}
});
Thread t1 = new Thread(new Runnable() {
public void run() {
while(socket1.isConnected())
{
Wait2();
try {
sendFile();
} catch (IOException e) {
e.printStackTrace();
}
}
}
});
t.start();
t1.start();
fis.close();
fis1.close();
out.close();
bis.close();
out1.close();
bis1.close();
socket.close();
socket1.close();
}
public void Wait2()
{
try {
Thread.currentThread().sleep(3000);
} catch (InterruptedException x) {
System.out.println("Interrupted!");
}
}
}
// class server
import java.io.*;
import java.net.*;
public class Server {
public void recivefile() throws IOException {
ServerSocket serverSocket = null;
ServerSocket serverSocket1 = null;
try {
serverSocket = new ServerSocket(4444);
//serverSocket1 = new ServerSocket(444);
} catch (IOException ex) {
System.out.println("Can't setup server on this port number. ");
}
try {
serverSocket1 = new ServerSocket(444);
} catch (IOException ex) {
System.out.println("Can't setup server on this port number. ");
}
Socket socket = null;
Socket socket1 = null;
InputStream is = null;
InputStream is1 = null;
FileOutputStream fos = null;
FileOutputStream fos1 = null;
BufferedOutputStream bos = null;
BufferedOutputStream bos1 = null;
int bufferSize = 0;
int bufferSize1 = 0;
try {
socket = serverSocket.accept();
socket1 = serverSocket1.accept();
} catch (IOException ex) {
System.out.println("Can't accept client connection. ");
}
try {
is = socket.getInputStream();
is1 = socket1.getInputStream();
bufferSize = socket.getReceiveBufferSize();
bufferSize1 = socket1.getReceiveBufferSize();
System.out.println("Buffer size: " + bufferSize);
System.out.println("file recieved");
System.out.println("Buffer size1: " + bufferSize1);
System.out.println("file recieved");
System.out.println("file recieved");
} catch (IOException ex) {
System.out.println("Can't get socket input stream. ");
}
try {
fos = new FileOutputStream("/home/reza/Desktop/reza");
bos = new BufferedOutputStream(fos);
fos1 = new FileOutputStream("/home/reza/Desktop/ali");
bos1 = new BufferedOutputStream(fos1);
} catch (FileNotFoundException ex) {
System.out.println("File not found. ");
}
byte[] bytes = new byte[bufferSize];
int count;
while ((count = is.read(bytes)) > 0) {
bos.write(bytes, 0, count);
}
byte[] bytes1 = new byte[bufferSize1];
int count1;
while ((count1 = is1.read(bytes1)) > 0) {
bos1.write(bytes1, 0, count1);
}
bos.flush();
bos.close();
bos1.flush();
bos1.close();
is.close();
is1.close();
socket.close();
serverSocket.close();
socket1.close();
serverSocket1.close();
}
public static void main(String[] args) throws IOException
{
System.out.println("server is run, please send file");
Server s = new Server();
s.recivefile();
}
}
error is :
Can't setup server on this port number.
Can't setup server on this port number.

You can't start a server on 127.0.0.2 - therein lies your problem.

netstat -ano | find "1024"
try above command if you are running your java files on windows environment that will help you to find any process using same port no as yours and also use
ex.printStackTrace() along with
System.out.println("Can't setup server on this port number.");

Assuming that your code runs on a unix platform, your server code is trying twice to open a socket on port 444, which is a system reserved port. In order to be able to succeed, your programme must run with administrative priviledges, and you must ensure that the port is not already used by another process.
A possible workaround is to:
use a port above 1024. These ports are free to use for userland programmes
in case of failure have a backup port, also above 1024. You must amend both server and client codes to try both ports, and of course your communication protocol must include some form of handshaking to make sure they are talking to the right interlocutor.
There are many other problems with your code listed in other answers.
you don't need to make every objects twice. Only one instance is enough in most cases,
if your server is running continuously and must accept many connections, you should not close the accepting socket at the end of one receiving session.
also the server is supposed to run a loop on the server socket accept call, and start a new thread for each incoming connection, whose job is to handle that connection.
While I understand your willingness to learn and experiment, there are existing solutions to what you are trying to achieve. For instance, you could simply use a FTP server for your purpose.

The way you have written client - server program is wrong I guess.
Following are the mistakes you have done...
1) In Client class, you have sendFile function in which you've created two threads - t & t1. In run function you are again calling the same sendFile function.
So it keeps creating threads under threads just like recursion.
2) In Server class, you are listening to two port within the same recieveFile function. As the socket = serverSocket.accept() is a blocking call, It wont excecute the rest of the code untill it finds a single client to connect.
So what exactly happens here is.. Once the first client connects, thenafter immediately it expects second client to connect.
In the mean time your client thread may try to access the port on which connection has not been established.
In short, your SERVER SHOULD BE IN A THREADING ENVIRONMENT NOT THE CLIENT.
And I would suggest that for different port you should use different server.
i.e. create different server class for both 1024 & 1025 port.