Input-/ouputStream hanging

Question

Hi all.
I'm having some trouble with sending an XML-file via outputstream.
I think the problem is, that the receiving part, a SAXBuilder, doesn't recognize any end of file in the incoming data, and therefore keeps reading. My assumption is based on the fact, that if the sender's outputstream is closed, the receiver reads everything just fine. Flushing the stream doesn't appear to have any effect.
How do I avoid this? Is it perhaps possible to communicate an EOF after sending the document?
ServerConnection (sender):
import java.io.*;
import java.net.*;
import java.net.InetAddress;
import java.util.ArrayList;
import fsr.universal_classes.Customer;
import java.math.BigDecimal;
import org.jdom.*;
import org.jdom.output.Format;
import org.jdom.output.XMLOutputter;
public class ServerConnection implements Runnable{
    private InetAddress hostname;
    private int portNumber;
    private Socket connection;
    private BufferedWriter out;
    private BufferedReader in;
    private boolean connected = false;
    private String threadName = "ServerConnection";
    public ServerConnection(){
        new Thread(this).start();
    @Override
    public void run(){
        connectToDatabase();
    private synchronized void connectToDatabase(){
        portNumber = 49352;
        try {
            hostname = InetAddress.getLocalHost();
        } catch (UnknownHostException ex) {
            threadMessage("Couldnt find local host");
        try {
            connection = new Socket(hostname, portNumber);
            connected = true;
            out = new BufferedWriter(new PrintWriter(connection.getOutputStream(),true));
            in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
        catch (IOException e) {
            System.out.println(e);
            connected = false;
    public ArrayList<Customer> getCustomers(){
        //  Create XML
        Element root = new Element("request");
        Element subject = new Element("subject");
        subject.setText("getAllCustomers");
        root.addContent(subject);
        // Create document and set DocType
        Document doc = new Document();
        doc.setRootElement(root);
        DocType xmlDoctype = new DocType("request", "src/commands.dtd");
        doc.setDocType(xmlDoctype);
        // Send XML
        XMLOutputter outputter = new XMLOutputter();
        outputter.setFormat(Format.getRawFormat());
        try {
            outputter.output(doc, out);
            out.flush();
        } catch (Exception e) {
            System.err.println("Exception: " + e);
        ArrayList<Customer> customersList = new ArrayList();
        return customersList;
    public void threadMessage(String message){
        System.out.println(threadName  + ": " + message);
Session (Receiver):
import java.net.*;
import java.io.*;
import fsr.server.exceptions.SessionStoppedException;
import org.jdom.Document;
import org.jdom.JDOMException;
import org.jdom.input.SAXBuilder;
public class Session implements Runnable{
    private Socket socket;
    private int id;
    private TCPServer tcpServer;
    private boolean connected = true;
    private SAXBuilder documentBuilder;
    private String threadName = "Session";
    public Session(Socket socket, int id) {
        this.tcpServer = TCPServer.getInstance();
     this.socket = socket;
        this.id = id;
        new Thread(this).start();
    @Override
    public void run() {
     try {
            communicate();
        catch(SessionStoppedException e){
            threadMessage("Session stopped: " + e.getError());
        catch(Throwable t){
            threadMessage("Session stopped (2)");
    public void communicate() throws SessionStoppedException {
        InputStreamReader ins;
        try {
            threadMessage("Getting input Stream");
            ins = new InputStreamReader(socket.getInputStream());
        catch (IOException e) {
            throw new SessionStoppedException("No info");
        while(connected){
            try {
                BufferedReader in = new BufferedReader(ins);
                threadMessage("Creating sax builder");
                documentBuilder = new SAXBuilder(true);
                threadMessage("Building document");
                Document doc = documentBuilder.build(in);
                System.out.println("Received: " + doc.toString());
                // If there are no well-formedness or validity errors,
                // then no exception is thrown.
                System.out.println(doc + " is valid.");
                System.out.println(doc.getRootElement().getName());
            // indicates a well-formedness or validity error
            catch (JDOMException e) {
                System.out.println( "is not valid.");
                System.out.println(e.getMessage());
            catch (IOException e) {
                System.out.println("Could not check " );
                System.out.println(" because " + e.getMessage());
            catch(Exception e){
                threadMessage("Error: " + e);
    public void threadMessage(String message){
        System.out.println(threadName + "(" + id + ")" + ": " + message);
}Thanks in advance.
Cheers,
Jonas

Answer 1

Jonas.Nielsen wrote:
I've been instructed, that there is no way to send a end of file.
What would probably help would be to send the size of the serialized document before sending the actual document. But how is that done?First, you should probably be using the stream directly, not wrapping it in a Writer, so you can write byte-oriented data. Then, if you knew the size of the document ahead of time, you could send the number of bytes as a long, followed by the document. If you don't know the number of bytes ahead of time, you could come up with some chunking protocol, where you would write the size of the chunk, followed by the chunk bytes. A chunk size of 0 could indicate EOF.
The DataOutputStream/DataInputStream wrapper classes can be of assistance here.