Communication between java and c++

[eekhoorn12]

Hey everyone

Me and a fellow student are writing a program which has to communicate with each other. His program is written in normal java and mine is written in C++ with Qt. I tried the Fortuneserver example to which he connected. We where able to connect but he didn't recieve any text. His out put was -1.

Could someone point me in the direction i have to look to make our programs work.

We are both working on windows (I run xp, he runs Vista) and i use Qt 4.3

[marcel]

The problem must be in the way he implemented the client. The fortune server works just fine with the client written with Qt...
http://java.sun.com/docs/books/tutor...ets/index.html

Could we see the code for the Java client?

Regards

[eekhoorn12]

I will post it here tommorow because he isn't available right now

[eekhoorn12]

Went wrong here.

[eekhoorn12]

Here is the java code for catching te message:

try
{ 
       socket = new Socket("145.92.14.112", 2911);  
       System.out.println("Socket Created");  
       out = new PrintWriter(socket.getOutputStream(), true); 
       in = new BufferedReader(new InputStreamReader(socket.getInputStream()));  
} 
 
catch (UnknownHostException e) 
{  
       System.out.println("Unknown host....");  
       System.exit(1);  
} 
 
catch  (IOException e) 
{  
       System.out.println("No I/O");  
       System.exit(1);  
} 
 
while(wii == 1)  
{  
     try
    {  
         if(in.readLine() != null)  
         {  
                //line = in.readLine();  
                System.out.println("Ontvangen: " + in.readLine()); 
         }  
     }  
 
    catch(IOException e)
    {  
         System.out.println("Read failed");  
         System.exit(-1);  
    }  
}

try
{ 
       socket = new Socket("145.92.14.112", 2911);  
       System.out.println("Socket Created");  
       out = new PrintWriter(socket.getOutputStream(), true); 
       in = new BufferedReader(new InputStreamReader(socket.getInputStream()));  
} 

catch (UnknownHostException e) 
{  
       System.out.println("Unknown host....");  
       System.exit(1);  
} 

catch  (IOException e) 
{  
       System.out.println("No I/O");  
       System.exit(1);  
} 

while(wii == 1)  
{  
     try
    {  
         if(in.readLine() != null)  
         {  
                //line = in.readLine();  
                System.out.println("Ontvangen: " + in.readLine()); 
         }  
     }  
    
    catch(IOException e)
    {  
         System.out.println("Read failed");  
         System.exit(-1);  
    }  
}

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[marcel]

I don't believe your client implementation is OK.
Read this first: http://java.sun.com/docs/books/tutor...entServer.html

EDIT: oh, now I see your code
Is the port OK? Otherwise it seems OK.
Have you debugged it? Does it throw any exceptions?

Regards

[marcel]

Does the client computer have a firewall?
If it has, try turning it off while you test.

Is the client started with administrator privileges? Maybe this helps a bit.

Regards

[wysota]

Don't you think you should wait until something connects and writes something to the socket? Does the Socket constructor wait until a connection is established and does it wait until something actually transmits data over the socket? In other words - are Socket() and getOutputStream() blocking?

[eekhoorn12]

We have editted de code a bit. We know have communication but the message he gets isn't exactly what i sent.

He gets a line but between each letter there is some null code.

The server code is the following:

/****************************************************************************
**
** Copyright (C) 2004-2007 Trolltech ASA. All rights reserved.
**
** This file is part of the example classes of the Qt Toolkit.
**
** This file may be used under the terms of the GNU General Public
** License version 2.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of
** this file.  Please review the following information to ensure GNU
** General Public Licensing requirements will be met:
** http://www.trolltech.com/products/qt/opensource.html
**
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://www.trolltech.com/products/qt/licensing.html or contact the
** sales department at sales@trolltech.com.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
****************************************************************************/
 
#include <QtGui>
#include <QtNetwork>
 
#include <stdlib.h>
 
#include "server.h"
 
Server::Server(QWidget *parent)
    : QDialog(parent)
{
    statusLabel = new QLabel;
    quitButton = new QPushButton(tr("Quit"));
    quitButton->setAutoDefault(false);
 
    tcpServer = new QTcpServer(this);
    tcpServer->listen(QHostAddress::Any,2911);
    if (!tcpServer->isListening()) {
        QMessageBox::critical(this, tr("Fortune Server"),
                              tr("Unable to start the server: %1.")
                              .arg(tcpServer->errorString()));
        close();
        return;
    }
 
    statusLabel->setText(tr("The server is running on port %1.\n"
                            "Run the Fortune Client example now.")
                         .arg(tcpServer->serverPort()));
 
    fortunes << tr("You've been leading a dog's life. Stay off the furniture.")
             << tr("You've got to think about tomorrow.")
             << tr("You will be surprised by a loud noise.")
             << tr("You will feel hungry again in another hour.")
             << tr("You might have mail.")
             << tr("You cannot kill time without injuring eternity.")
             << tr("Computers are not intelligent. They only think they are.");
 
    connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));
    connect(tcpServer, SIGNAL(newConnection()), this, SLOT(sendFortune()));
 
    QHBoxLayout *buttonLayout = new QHBoxLayout;
    buttonLayout->addStretch(1);
    buttonLayout->addWidget(quitButton);
    buttonLayout->addStretch(1);
 
    QVBoxLayout *mainLayout = new QVBoxLayout;
    mainLayout->addWidget(statusLabel);
    mainLayout->addLayout(buttonLayout);
    setLayout(mainLayout);
 
    setWindowTitle(tr("Fortune Server"));
}
 
void Server::sendFortune()
{
    QByteArray block;
    statusLabel->setText("Bla");
    QDataStream out(&block, QIODevice::WriteOnly);
    //out.setVersion(QDataStream::Qt_4_0);
    //out << (quint16)0;
    out << fortunes.at(qrand() % fortunes.size());
    //out.device()->seek(0);
    //out << (quint16)(block.size() - sizeof(quint16));
 
    QTcpSocket *clientConnection = tcpServer->nextPendingConnection();
    connect(clientConnection, SIGNAL(disconnected()),
            clientConnection, SLOT(deleteLater()));
 
    clientConnection->write(block);
    clientConnection->disconnectFromHost();
}

/****************************************************************************
**
** Copyright (C) 2004-2007 Trolltech ASA. All rights reserved.
**
** This file is part of the example classes of the Qt Toolkit.
**
** This file may be used under the terms of the GNU General Public
** License version 2.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of
** this file.  Please review the following information to ensure GNU
** General Public Licensing requirements will be met:
** http://www.trolltech.com/products/qt/opensource.html
**
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://www.trolltech.com/products/qt/licensing.html or contact the
** sales department at sales@trolltech.com.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
****************************************************************************/

#include <QtGui>
#include <QtNetwork>

#include <stdlib.h>

#include "server.h"

Server::Server(QWidget *parent)
    : QDialog(parent)
{
    statusLabel = new QLabel;
    quitButton = new QPushButton(tr("Quit"));
    quitButton->setAutoDefault(false);

    tcpServer = new QTcpServer(this);
    tcpServer->listen(QHostAddress::Any,2911);
    if (!tcpServer->isListening()) {
        QMessageBox::critical(this, tr("Fortune Server"),
                              tr("Unable to start the server: %1.")
                              .arg(tcpServer->errorString()));
        close();
        return;
    }

    statusLabel->setText(tr("The server is running on port %1.\n"
                            "Run the Fortune Client example now.")
                         .arg(tcpServer->serverPort()));

    fortunes << tr("You've been leading a dog's life. Stay off the furniture.")
             << tr("You've got to think about tomorrow.")
             << tr("You will be surprised by a loud noise.")
             << tr("You will feel hungry again in another hour.")
             << tr("You might have mail.")
             << tr("You cannot kill time without injuring eternity.")
             << tr("Computers are not intelligent. They only think they are.");

    connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));
    connect(tcpServer, SIGNAL(newConnection()), this, SLOT(sendFortune()));
    
    QHBoxLayout *buttonLayout = new QHBoxLayout;
    buttonLayout->addStretch(1);
    buttonLayout->addWidget(quitButton);
    buttonLayout->addStretch(1);

    QVBoxLayout *mainLayout = new QVBoxLayout;
    mainLayout->addWidget(statusLabel);
    mainLayout->addLayout(buttonLayout);
    setLayout(mainLayout);

    setWindowTitle(tr("Fortune Server"));
}

void Server::sendFortune()
{
    QByteArray block;
    statusLabel->setText("Bla");
    QDataStream out(&block, QIODevice::WriteOnly);
    //out.setVersion(QDataStream::Qt_4_0);
    //out << (quint16)0;
    out << fortunes.at(qrand() % fortunes.size());
    //out.device()->seek(0);
    //out << (quint16)(block.size() - sizeof(quint16));

    QTcpSocket *clientConnection = tcpServer->nextPendingConnection();
    connect(clientConnection, SIGNAL(disconnected()),
            clientConnection, SLOT(deleteLater()));

    clientConnection->write(block);
    clientConnection->disconnectFromHost();
}

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and the java code is the following:

try 
{  
     while ((fromServer = in.readLine()) != null) 
    {  
            System.out.println("Server: " + fromServer);  
            if (fromServer.equals("Bye.")) 
                break;  
 
            fromUser = stdIn.readLine();  
 
            if (fromUser != null)
            {  
                System.out.println("Client: " + fromUser); 
                out.println(fromUser);  
            }  
      }  
}  
 
catch (IOException e) 
{  
        System.err.println("Couldn't get I/O for the connection to: taranis.");  
         System.exit(1);  
}

try 
{  
     while ((fromServer = in.readLine()) != null) 
    {  
            System.out.println("Server: " + fromServer);  
            if (fromServer.equals("Bye.")) 
                break;  
     
            fromUser = stdIn.readLine();  

            if (fromUser != null)
            {  
                System.out.println("Client: " + fromUser); 
                out.println(fromUser);  
            }  
      }  
}  

catch (IOException e) 
{  
        System.err.println("Couldn't get I/O for the connection to: taranis.");  
         System.exit(1);  
}

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[wysota]

You are experiencing differences in data encoding. Make sure you write and read data that is encoded the same way. Especially if you use QDataStream.