Problem with simple TCP chat client-server

Hi, im new in QT. I have QT 5.5 and i create a very simple chat client-server based on TCP. But when i clicked button on server window to send message, application crashed. Client aplication doesn't get any errors, so i think it's working. I dont know how to fix it :/

Thanks for any reply!!

This is my code that i made:
server.pro

Code:

#-------------------------------------------------
#
# Project created by QtCreator 2016-01-17T12:45:39
#
#-------------------------------------------------
 
QT       += core gui
QT       += network
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
 
TARGET = server
TEMPLATE = app
 
 
SOURCES += main.cpp\
        server.cpp
 
HEADERS  += server.h
 
FORMS    += server.ui

server.h

Code:

#ifndef SERVER_H
#define SERVER_H
 
#include <QMainWindow>
#include <QTcpServer>
#include <QTcpSocket>
#include <QHostAddress>
#include <QList>
 
namespace Ui {
class server;
}
 
class server : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit server(QWidget *parent = 0);
    ~server();
 
public slots:
    void connect_new();
    void leer_socketclient();
 
private slots:
    void on_pushButton_clicked();
 
private:
    Ui::server *ui;
    QTcpServer *tcpserver;
    QTcpSocket *tcpclient;
};
 
#endif // SERVER_H

server.cpp

Code:

#include "server.h"
#include "ui_server.h"
 
server::server(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::server)
{
    ui->setupUi(this);
 
    tcpserver = new QTcpServer (this);
    tcpserver->newConnection();
 
    tcpserver->listen(QHostAddress::LocalHost, 1234);
    connect(tcpserver, SIGNAL(newConnection()), this, SLOT(connect_new()));
}
 
server::~server()
{
    delete ui;
}
 
void server::connect_new()
{
    tcpclient = tcpserver->nextPendingConnection();
    connect(tcpclient, SIGNAL(readyRead()), this, SLOT(leer_socketclient()));
}
 
void server::leer_socketclient()
{
    QByteArray buffer;
    buffer.resize( tcpclient->bytesAvailable() );
    tcpclient->read( buffer.data(), buffer.size() );
    ui->plainTextEdit->setReadOnly( true );
    ui->plainTextEdit->appendPlainText( QString (buffer));
}
 
void server::on_pushButton_clicked()
{
    tcpclient->write( ui->lineEdit->text().toLatin1().data(), ui->lineEdit->text().size());
    ui->lineEdit->clear();
}

main.cpp

Code:

#include "server.h"
#include <QApplication>
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    server w;
    w.show();
 
    return a.exec();
}

=========================================
and client if you check

client.pro

Code:

#-------------------------------------------------
#
# Project created by QtCreator 2016-01-17T12:22:05
#
#-------------------------------------------------
 
QT       += core gui
QT       += network
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
 
TARGET = client
TEMPLATE = app
 
 
SOURCES += main.cpp\
        client.cpp
 
HEADERS  += client.h
 
FORMS    += client.ui

client.h

Code:

#ifndef CLIENT_H
#define CLIENT_H
 
#include <QMainWindow>
#include <QTcpSocket>
#include <QHostAddress>
#include <QList>
 
namespace Ui {
class client;
}
 
class client : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit client(QWidget *parent = 0);
    ~client();
 
 
private slots:
    void on_pushButton_clicked();
 
public slots:
    void leer_socketserver();
 
private:
    Ui::client *ui;
 
    QTcpSocket *tcpclient;
};
 
#endif // CLIENT_H

client.cpp

Code:

#include "client.h"
#include "ui_client.h"
 
client::client(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::client)
{
    ui->setupUi(this);
 
    tcpclient = new QTcpSocket (this);
 
    tcpclient->connectToHost( QHostAddress::LocalHost , 1234);
 
    connect (tcpclient, SIGNAL (readyRead()), this, SLOT (leer_socketserver()));
}
 
client::~client()
{
    delete ui;
}
 
void client::on_pushButton_clicked()
{
    tcpclient->write( ui->lineEdit->text().toLatin1().data(), ui->lineEdit->text().size());
    ui->lineEdit->clear();
}
 
void client::leer_socketserver()
{
    QByteArray buffer;
    buffer.resize( tcpclient->bytesAvailable() );
    tcpclient->read( buffer.data(), buffer.size() );
    ui->plainTextEdit->setReadOnly( true );
    ui->plainTextEdit->appendPlainText( QString (buffer));
}

main.cpp

Code:

#include "client.h"
#include <QApplication>
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    client w;
    w.show();
 
    return a.exec();
}

=========================
server.ui

Code:

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>server</class>
 <widget class="QMainWindow" name="server">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>376</width>
    <height>335</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>server</string>
  </property>
  <widget class="QWidget" name="centralWidget">
   <widget class="QLineEdit" name="lineEdit">
    <property name="geometry">
     <rect>
      <x>100</x>
      <y>200</y>
      <width>261</width>
      <height>20</height>
     </rect>
    </property>
   </widget>
   <widget class="QLabel" name="label">
    <property name="geometry">
     <rect>
      <x>10</x>
      <y>200</y>
      <width>91</width>
      <height>16</height>
     </rect>
    </property>
    <property name="text">
     <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;&lt;span style=&quot; font-size:11pt;&quot;&gt;Wiadomosc:&lt;/span&gt;&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
    </property>
   </widget>
   <widget class="QLabel" name="label_2">
    <property name="geometry">
     <rect>
      <x>20</x>
      <y>10</y>
      <width>91</width>
      <height>16</height>
     </rect>
    </property>
    <property name="text">
     <string>Chat</string>
    </property>
   </widget>
   <widget class="QPushButton" name="pushButton">
    <property name="geometry">
     <rect>
      <x>250</x>
      <y>230</y>
      <width>111</width>
      <height>23</height>
     </rect>
    </property>
    <property name="text">
     <string>Wyslij na client</string>
    </property>
   </widget>
   <widget class="QPlainTextEdit" name="plainTextEdit">
    <property name="geometry">
     <rect>
      <x>20</x>
      <y>30</y>
      <width>341</width>
      <height>151</height>
     </rect>
    </property>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menuBar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>376</width>
     <height>21</height>
    </rect>
   </property>
  </widget>
  <widget class="QToolBar" name="mainToolBar">
   <attribute name="toolBarArea">
    <enum>TopToolBarArea</enum>
   </attribute>
   <attribute name="toolBarBreak">
    <bool>false</bool>
   </attribute>
  </widget>
  <widget class="QStatusBar" name="statusBar"/>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <resources/>
 <connections/>
</ui>

Re: Problem with simple TCP chat client-server

Are you sure server::tcpclient is a valid pointer when you call functions on it in the slot connected to the button?

Better initialize to 0 and check for != 0

Also no need to call signal "newConnection" in line 11 of the server constructor.

Cheers,
_

Re: Problem with simple TCP chat client-server

After 6 hours i figured what i made wrong.
In server.cpp
Code:

tcpserver->newConnection();
That line is wrong.

It's should be that
Code:

tcpserver->setMaxPendingConnections(1); //and add this line tcpclient = new QTcpSocket (this);
@Edit
But now, a message doesn't send to anyone( client->server | server -> client)

mhm...

@Edit 2
Now that i mentioned, if i delete this line
Code:

tcpserver->setMaxPendingConnections(1);
message is sending.

But, only with 1 pc :/

If i tried on 2 pc connected to one router, server side get me this:
Code:

QIODevice::write (QTcpSocket): device not open
in Application Output

Any ideas?

Re: Problem with simple TCP chat client-server

Quote:
Originally Posted by ziele
Code:

tcpserver->newConnection();
That line is wrong.
Yes, as I said :)
Quote:
Originally Posted by ziele
It's should be that
Code:

//and add this line tcpclient = new QTcpSocket (this);
No, because you don't want to connect to clients but accept client connections

Quote:

Originally Posted by ziele

But, only with 1 pc :/

Yes, because your handler for newConnection() overwrites a single QTcpSocket variable.

Quote:

Originally Posted by ziele

Any ideas?

Yes, store the accepted connections in a list or map, not in a single pointer variable.

Cheers,
_

Re: Problem with simple TCP chat client-server

I figured a solution.
I made a server to accept connect to any client not only localhost, and in client instead of localhost i connect to ip 192.168....
And that work on 2 different PC on same LAN. THANKS FOR HELP :)