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IndexOutOfBoundsException when transferring a file through sockets. urgent data transfer control

How can I resolve this error when transferring a file through sockets:
java.lang.IndexOutOfBoundsException
at java.io.FileOutputStream.writeBytes(Native Method)
at java.io.FileOutputStream.write(FileOutputStream.java:326)
at Client.getFile(Client.java:18)
I implemented a client server application for transferring a file using the TCP protocol. Server is parallel. It is also necessary to implement transmission control using urgent data. I did not find a solution on Java on the Internet.
Class Server:
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
public class Server {
private ServerSocket serverSocket;
public void start(int port) throws IOException {
serverSocket = new ServerSocket(port);
while (true)
new ClientHandler(serverSocket.accept()).start();
}
public void stop() throws IOException{
serverSocket.close();
}
private static class ClientHandler extends Thread {
private Socket clientSocket;
private DataOutputStream out;
private FileInputStream in;
public ClientHandler(Socket socket) {
this.clientSocket = socket;
}
public void run() {
try {
out = new DataOutputStream(clientSocket.getOutputStream());
out.writeInt((int) Prop.FILE_1.length());
} catch (IOException e) {
e.printStackTrace();
}
try {
in = new FileInputStream(Prop.FILE_1);
} catch (IOException e) {
e.printStackTrace();
}
while (true) {
byte buf[] = new byte[512];
int len = 0;
try {
len = in.read(buf);
} catch (IOException e) {
e.printStackTrace();
}
if(len == -1) {
break;
}
try {
out.write(buf, 0, len);
} catch (IOException e) {
e.printStackTrace();
}
try {
out.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
/*try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
clientSocket.close();
} catch (IOException e) {
e.printStackTrace();
}*/
}
}
}
Class Client:
import java.io.*;
import java.net.Socket;
public class Client {
private Socket clientSocket;
private FileOutputStream out;
private DataInputStream in;
public String getFile() throws IOException {
int i = 0;
int len;
byte buf[] = new byte[512];
Integer fileSize;
fileSize = in.readInt();
while (i < fileSize) {
len = in.read(buf);
if (len == -1) {
break;
}
i += len;
out.write(buf, 0, len);
out.flush();
}
out.close();
return in.readUTF();
}
public void startConnection(String ip, int port) throws IOException {
clientSocket = new Socket(ip, port);
out = new FileOutputStream(Prop.FILE_2);
in = new DataInputStream(clientSocket.getInputStream());
}
public void stopConnection() throws IOException {
in.close();
out.close();
clientSocket.close();
}
}
Test
public class TestCS {
#Test
// (threadPoolSize = 3, invocationCount = 6, timeOut = 1000)
public void givenClient1__whenServerResponds__thenCorrect() throws IOException {
SoftAssert softAssert = new SoftAssert();
Client client1 = new Client();
client1.startConnection("127.0.0.1", 555);
String file = client1.getFile();
System.out.println(file);
client1.stopConnection();
softAssert.assertEquals(file, "First file!!!");
softAssert.assertAll();
}
}

You are reading InputStream wrongly. The logic you are trying to put there is already available in DataInputStream.read(..) method. All you have to do is to check how many bytes it read from the stream.
Change your while loop in Client like this
while (i < fileSize) {
// javadoc for below : - https://docs.oracle.com/javase/7/docs/api/java/io/DataInputStream.html#read(byte[])
len = in.read(buf);
if(len<0) {
break;
}
i += len;
out.write(buf, 0, len);
out.flush();
}
Note : I have not checked your logic. All I checked and corrected is the Exception you got.
Also, typically we do not read fileSize upfront. You generally keep on reading stream till you get EOF (-1) from the stream. Please check that logic as well.

Network communication isn´t working

I made a little game. Now i want to get the highscore from my Server. The code on the client:
private int getOnlineHighscore() {
int highscore = 0;
try {
socket = new Socket("localhost", 444);
input = socket.getInputStream();
System.out.println(input);
highscore = input.read();
input.close();
socket.close();
input = null;
socket = null;
} catch (Exception e) {
System.out.println("Verbindung fehlgeschlagen!");
}
System.out.println(highscore);
return highscore;
}
And on the Server:
import java.io.*;
import java.net.*;
public class ReadServer extends Thread {
private Socket socket;
public ReadServer(Socket socket) {
super();
this.socket = socket;
}
public void run() {
try {
System.out.println(socket.getInetAddress());
String result = "";
try (BufferedReader br = new BufferedReader(
new FileReader(System.getProperty("user.home") + "/AppData/Roaming/GameServer/.sg"))) {
StringBuilder sb = new StringBuilder();
String line = br.readLine();
System.out.println("2");
while (line != null) {
sb.append(line);
sb.append(System.lineSeparator());
line = br.readLine();
}
System.out.println("3");
result = sb.toString();
System.out.println("3.5");
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("4");
socket.getOutputStream().write(Integer.parseInt(result));
System.out.println(result);
} catch (Exception e) {
}
try {
socket.close();
} catch (Exception e) {
}
}
public static void main(String[] Args) {
Socket socket = null;
ServerSocket server = null;
try {
server = new ServerSocket(444);
while (true) {
socket = server.accept();
new ReadServer(socket).start();
}
} catch (Exception e) {
}
try {
server.close();
} catch (Exception e) {
}
}
}
If I run it, the client function returns:
-1
The server writes in the console(not important I think):
/127.0.0.1
2
3
3.5
4
How to solve the problem? I want to send an int stored on my Server to a client.
-Jakob

-1 is returned by read() to specify end of stream , make sure data to be read is being returned .

What is the highscore stored in the file? I believe the file is empty and it fails on parsing the integer but as your catch block is empty, you don't see the exception. Put printStacktrace or rethrow.
Another problem is that OutputStream sends only bytes and therefore write method sends only low 8 bits. To send int wrap the stream with DataOutputStream and DataInputStream on the client side.

Why it is refusing the connection for second time?

I am trying to forward a message from a client to a server and again from that server to another server. For the first time it works fine but when I type second message its say "Unexpected exception: Connection refused" why is it so?
Here is the code
Client.java
import java.net.*;
import java.io.*;
public class Client {
private Socket socket = null;
private DataInputStream console = null;
private DataOutputStream streamOut = null;
#SuppressWarnings("deprecation")
public Client(String serverName, int serverPort) {
System.out.println("Establishing connection. Please wait ...");
try {
socket = new Socket(serverName, serverPort);
System.out.println("Connected: " + socket);
start();
} catch (UnknownHostException uhe) {
System.out.println("Host unknown: " + uhe.getMessage());
} catch (IOException ioe) {
System.out.println("Unexpected exception: " + ioe.getMessage());
}
String line = "";
while (!line.equals("exit")) {
try {
line = console.readLine();
streamOut.writeUTF(line);
streamOut.flush();
} catch (IOException ioe) {
System.out.println("Sending error: " + ioe.getMessage());
}
}
}
public void start() throws IOException {
console = new DataInputStream(System.in);
streamOut = new DataOutputStream(socket.getOutputStream());
}
public void stop() {
try {
if (console != null)
console.close();
if (streamOut != null)
streamOut.close();
if (socket != null)
socket.close();
} catch (IOException ioe) {
System.out.println("Error closing ...");
}
}
public static void main(String args[]) {
#SuppressWarnings("unused")
Client client = null;
if (args.length != 2)
System.out.println("Usage: java Client host port");
else
client = new Client(args[0], Integer.parseInt(args[1]));
}
}
AuServer.java
import java.net.*;
import java.io.*;
public class AuServer {
private Socket socket = null;
private Socket publishingsocket = null;
private ServerSocket server = null;
private DataInputStream streamIn = null;
private String line = null;
private DataOutputStream streamOut = null;
public AuServer(int port) {
try {
System.out.println("Binding to port " + port + ", please wait ...");
server = new ServerSocket(port);
System.out.println("Server started: " + server);
System.out.println("Waiting for a client ...");
socket = server.accept();
System.out.println("Client accepted: " + socket);
open();
boolean done = false;
while (!done) {
try {
line = streamIn.readUTF();
System.out.println(line);
done = line.equals("exit");
} catch (IOException ioe) {
done = true;
}
forward(line, 50090);
}
close();
} catch (IOException ioe) {
System.out.println(ioe);
}
}
public void forward(String line, int port) {
try {
publishingsocket = new Socket("localhost", port);
streamOut = new DataOutputStream(publishingsocket.getOutputStream());
streamOut.writeUTF(line);
streamOut.flush();
} catch (UnknownHostException uhe) {
System.out.println("Host unknown: " + uhe.getMessage());
} catch (IOException ioe) {
System.out.println("Unexpected exception: " + ioe.getMessage());
} finally {
try {
publishingsocket.close();
} catch (IOException e) {
System.out.println(e.getMessage());
}
}
}
public void open() throws IOException {
streamIn = new DataInputStream(new BufferedInputStream(
socket.getInputStream()));
}
public void close() throws IOException {
if (socket != null)
socket.close();
if (streamIn != null)
streamIn.close();
}
public static void main(String args[]) {
#SuppressWarnings("unused")
AuServer server = null;
if (args.length != 1)
System.out.println("Usage: java Server port");
else
server = new AuServer(Integer.parseInt(args[0]));
}
}
AppServer.java
import java.net.*;
import java.io.*;
public class AppServer {
private Socket socket = null;
private ServerSocket server = null;
private DataInputStream streamIn = null;
public AppServer(int port) {
try {
System.out.println("Binding to port " + port + ", please wait ...");
server = new ServerSocket(port);
System.out.println("Server started: " + server);
System.out.println("Waiting for a client ...");
socket = server.accept();
System.out.println("Client accepted: " + socket);
open();
boolean done = false;
while (!done) {
try {
String line = streamIn.readUTF();
System.out.println(line);
done = line.equals("exit");
} catch (IOException ioe) {
done = true;
}
}
close();
} catch (IOException ioe) {
System.out.println(ioe);
}
}
public void open() throws IOException {
streamIn = new DataInputStream(new BufferedInputStream(
socket.getInputStream()));
}
public void close() throws IOException {
if (socket != null)
socket.close();
if (streamIn != null)
streamIn.close();
}
public static void main(String args[]) {
#SuppressWarnings("unused")
AppServer server = null;
server = new AppServer(50090);
}
}
Pls help............

A typically socket server would require some kind of loop where in the server socket would accept incoming connections and spawn a new Thread which would be responsible for actually handling the new Socket connection, leaving the current thread free to continue processing any new incoming connections, for example...
server = new ServerSocket(port);
while (continueAccpetingConnections) {
Socket socket = server.accept();
Thread thread = new Thread(new SocketHandler(socket));
thread.start();
}
The SocketHandler would implement Runnable and provide a constructor that would accept a Socket variable.
It would then be the responsibility of the SocketHandler to actually perform the communications required by the server.
Now, if you wanted to have only one active connection, you might use
while (continueAccpetingConnections) {
Socket socket = server.accept();
process(socket);
}
Which would prevent any new connections until process returned...

Your server is written to accept exactly one connection, process it in the same thread, and then exit. If you want to keep accepting connections, do so, in a loop. If you want to handle clients concurrently, start a new thread to handle each accepted socket.

BufferedReader from server does not work

In this code I can correctly receive a request using BufferedReader inClient, created on the client socket.
Then I send the request to the server and I see the server gets it.
But then, when I try to read the reply from the server (using BufferedReader inServer on the socket of the server), it always ends in IOException: Impossible read from server.
I am referring to the block ################
Do you know any possible reasons?
import java.io.*;
import java.net.Socket;
import java.net.ServerSocket;
import java.net.InetAddress;
import java.net.UnknownHostException;
public class ProxyMain {
public static void main(String argv[]) {
int proxyPort = 55554;
String proxyAddr = "127.0.0.1";
ServerSocket proxySocket = null;
try {
proxySocket = new ServerSocket(proxyPort, 50, InetAddress.getByName("127.0.0.1"));
}
catch (Exception e) {
System.err.println("Impossible to create socket server!");
System.out.flush();
System.exit(1);
}
System.out.printf("Proxy active on port: %d and on address %s\n", proxyPort, proxySocket.getInetAddress());
System.out.println();
while (true) {
Socket client = null;
Socket sockServ = null;
BufferedReader inClient = null;
PrintWriter outClient = null;
BufferedReader inServer = null;
PrintWriter outServer = null;
String request = new String();
String tmp = new String();
String reply = new String();
String tmpReply = new String();
try {
client = proxySocket.accept();
System.out.println("Connected to: ");
System.out.println(client.getInetAddress().toString());
System.out.printf("On port %d\n", client.getPort());
System.out.println();
inClient = new BufferedReader(new InputStreamReader(client.getInputStream()));
outClient = new PrintWriter(client.getOutputStream(), true);
}
/*catch (IOException e) {
System.err.println("Couldn't get I/O for connection accepted");
System.exit(1);
}*/
catch (Exception e) {
System.out.println("Error occurred!");
System.exit(1);
}
System.out.println("Received request:");
try{
for (int i = 0; i<2; i++) {
tmp = inClient.readLine();
request = request + tmp;
}
inClient.close();
}
catch (IOException ioe) {
System.err.println("Impossible to read mhttp request!");
System.exit(1);
}
System.out.println(request);
System.out.println();
try {
sockServ = new Socket("127.0.0.1", 55555);
outServer = new PrintWriter(sockServ.getOutputStream(), true);
inServer = new BufferedReader(new InputStreamReader(sockServ.getInputStream()));
}
catch (UnknownHostException e) {
System.err.println("Don't know about host: 127.0.0.1:55555");
System.exit(1);
}
catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to: 127.0.0.1:55555");
System.exit(1);
}
outServer.println(request);
outServer.close();
try {
#################################################
while ((tmpReply = inServer.readLine()) != null) {
System.out.println(tmpReply);
reply = reply + tmpReply;
}
inServer.close();
sockServ.close();
}
catch (IOException ioe) {
System.err.println("Impossible to read from server!");
System.exit(1);
}
outClient.println(reply);
outClient.close();
try {
client.close();
}
catch (IOException ioe) {
System.err.printf("Impossible to close connection with %s:%d\n", client.getInetAddress().toString(), client.getPort());
}
}
}
}
UPDATE:
It seems that if I do:
boolean res = inServer.ready();
it always return false.
So Server is not ready to send the reply but this is strange...with my Project in C e Python it worked immediately. Why should java be different?

When you close outServer, you close the underlying socket. if you just want to close the output and keep the input open, you need to use Socket.shutdownOutput(). note, you have the same problem when you close inClient.

This works, maybe you can get some ideas from it...
ChatServer - broadcasts to all connected clients
In one command prompt: java ChartServer
In another: java ChatClient localhost (or the ip address of where the server is running)
And another: java ChatClient localhost (or the ip address of where the server is running)
Start chatting in the client windows.
Server like this...
// xagyg wrote this, but you can copy it
import java.io.*;
import java.net.*;
import java.util.*;
public class ChatServer {
public static List list = new ArrayList();
public static void main(String[] args) throws Exception {
ServerSocket svr = new ServerSocket(4444);
System.out.println("Chat Server started!");
while (true) {
try {
Socket s = svr.accept();
synchronized(list) {
list.add(s);
}
new Handler(s, list).start();
}
catch (IOException e) {
// print out the error, but continue!
System.err.println(e);
}
}
}
}
class Handler extends Thread {
private Socket s;
private String ipaddress;
private List list;
Handler (Socket s, List list) throws Exception {
this.s = s;
ipaddress = s.getInetAddress().toString();
this.list = list;
}
public void run () {
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(s.getInputStream()));
String message;
//MyDialog x = (MyDialog)map.get(ipaddress.substring(1));
while ((message = reader.readLine()) != null) {
if (message.equals("quit")) {
synchronized(list) {
list.remove(s);
}
break;
}
synchronized(list) {
for (Object object: list) {
Socket socket = (Socket)object;
if (socket==s) continue;
PrintWriter writer = new PrintWriter(socket.getOutputStream());
writer.println(ipaddress + ": " + message);
writer.flush();
}
}
}
try { reader.close(); } catch (Exception e) {}
}
catch (Exception e) {
System.err.println(e);
}
}
}
Client like this ...
// xagyg wrote this, but you can copy it
import java.util.*;
import java.io.*;
import java.net.*;
public class ChatClient {
public static void main(String[] args) throws Exception {
Socket s = new Socket(args[0], 4444);
BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));
PrintWriter out = new PrintWriter(s.getOutputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String message;
new SocketReader(in).start();
while ((message = reader.readLine())!=null) {
out.println(message);
out.flush();
if (message.equals("quit")) break;
}
in.close();
out.close();
}
}
class SocketReader extends Thread {
BufferedReader in;
public SocketReader(BufferedReader in) {
this.in = in;
}
public void run() {
String message;
try {
while ((message = in.readLine())!=null) {
System.out.println(message);
}
}
catch (Exception e) {
throw new RuntimeException(e);
}
}
}

Java Sockets - A Client that reads the data the server gets

I am working on a java socket program and have difulcites with the client part. The server get's what all the clients write, but the client only gets what it writes. Could someone provide me with an example of a client part of a program that gets what all the clients write? Thanks!

Here is an "echo server" example
import java.io.*;
import java.net.*;
class TCPServer
{
public static void main(String argv[]) throws IOException
{
ServerSocket serverSocket = null;
DataInputStream serverInput = null;
PrintStream serverOutput = null;
String line = null;
Socket clientSocket = null;
// create server socket
try
{
serverSocket = new ServerSocket(2012);
clientSocket = serverSocket.accept();
serverInput = new DataInputStream(clientSocket.getInputStream());
serverOutput = new PrintStream(clientSocket.getOutputStream());
}
catch(IOException e){System.out.println(e);}
// receive data and send it back to the client
try
{
while(true)
{
line = serverInput.readLine();
if(line.equals("exit"))
{
break;
}
else
{
if(!line.equals(null) && !line.equals("exit"))
{
System.out.println("Received " +line);
line = line+" MODIFIED";
serverOutput.println(line);
}
}
}
}
catch(IOException e){System.out.println("SERVER SIDE: Unable send/receive data");}
try
{
serverInput.close();
serverOutput.close();
clientSocket.close();
serverSocket.close();
}
catch(IOException e){System.out.println(e);}
}
}
Here is the client
import java.io.*;
import java.net.*;
public class TCPClient
{
public static void main(String[] args) throws IOException
{
Socket echoSocket = null;
PrintWriter out = null;
BufferedReader in = null;
try {
echoSocket = new Socket("localhost", 2012);
out = new PrintWriter(echoSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(echoSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Don't know about host");
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O");
System.exit(1);
}
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
String userInput;
while ((userInput = stdIn.readLine()) != null) {
out.println(userInput);
System.out.println("echo: " + in.readLine());
if(userInput.equals("exit"))
break;
}
out.close();
in.close();
stdIn.close();
echoSocket.close();
}
}