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
Qt Code: 
  1. #-------------------------------------------------
  2. #
  3. # Project created by QtCreator 2016-01-17T12:45:39
  4. #
  5. #-------------------------------------------------
  6.  
  7. QT       += core gui
  8. QT       += network
  9. greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
  10.  
  11. TARGET = server
  12. TEMPLATE = app
  13.  
  14.  
  15. SOURCES += main.cpp\
  16.         server.cpp
  17.  
  18. HEADERS  += server.h
  19.  
  20. FORMS    += server.ui
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server.h
Qt Code: 
  1. #ifndef SERVER_H
  2. #define SERVER_H
  3.  
  4. #include <QMainWindow>
  5. #include <QTcpServer>
  6. #include <QTcpSocket>
  7. #include <QHostAddress>
  8. #include <QList>
  9.  
  10. namespace Ui {
  11. class server;
  12. }
  13.  
  14. class server : public QMainWindow
  15. {
  16.     Q_OBJECT
  17.  
  18. public:
  19.     explicit server(QWidget *parent = 0);
  20.     ~server();
  21.  
  22. public slots:
  23.     void connect_new();
  24.     void leer_socketclient();
  25.  
  26. private slots:
  27.     void on_pushButton_clicked();
  28.  
  29. private:
  30.     Ui::server *ui;
  31.     QTcpServer *tcpserver;
  32.     QTcpSocket *tcpclient;
  33. };
  34.  
  35. #endif // SERVER_H
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server.cpp
Qt Code: 
  1. #include "server.h"
  2. #include "ui_server.h"
  3.  
  4. server::server(QWidget *parent) :
  5.     QMainWindow(parent),
  6.     ui(new Ui::server)
  7. {
  8.     ui->setupUi(this);
  9.  
  10.     tcpserver = new QTcpServer (this);
  11.     tcpserver->newConnection();
  12.  
  13.     tcpserver->listen(QHostAddress::LocalHost, 1234);
  14.     connect(tcpserver, SIGNAL(newConnection()), this, SLOT(connect_new()));
  15. }
  16.  
  17. server::~server()
  18. {
  19.     delete ui;
  20. }
  21.  
  22. void server::connect_new()
  23. {
  24.     tcpclient = tcpserver->nextPendingConnection();
  25.     connect(tcpclient, SIGNAL(readyRead()), this, SLOT(leer_socketclient()));
  26. }
  27.  
  28. void server::leer_socketclient()
  29. {
  30.     QByteArray buffer;
  31.     buffer.resize( tcpclient->bytesAvailable() );
  32.     tcpclient->read( buffer.data(), buffer.size() );
  33.     ui->plainTextEdit->setReadOnly( true );
  34.     ui->plainTextEdit->appendPlainText( QString (buffer));
  35. }
  36.  
  37. void server::on_pushButton_clicked()
  38. {
  39.     tcpclient->write( ui->lineEdit->text().toLatin1().data(), ui->lineEdit->text().size());
  40.     ui->lineEdit->clear();
  41. }
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main.cpp
Qt Code: 
  1. #include "server.h"
  2. #include <QApplication>
  3.  
  4. int main(int argc, char *argv[])
  5. {
  6.     QApplication a(argc, argv);
  7.     server w;
  8.     w.show();
  9.  
  10.     return a.exec();
  11. }
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=========================================
and client if you check

client.pro
Qt Code: 
  1. #-------------------------------------------------
  2. #
  3. # Project created by QtCreator 2016-01-17T12:22:05
  4. #
  5. #-------------------------------------------------
  6.  
  7. QT       += core gui
  8. QT       += network
  9. greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
  10.  
  11. TARGET = client
  12. TEMPLATE = app
  13.  
  14.  
  15. SOURCES += main.cpp\
  16.         client.cpp
  17.  
  18. HEADERS  += client.h
  19.  
  20. FORMS    += client.ui
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client.h
Qt Code: 
  1. #ifndef CLIENT_H
  2. #define CLIENT_H
  3.  
  4. #include <QMainWindow>
  5. #include <QTcpSocket>
  6. #include <QHostAddress>
  7. #include <QList>
  8.  
  9. namespace Ui {
  10. class client;
  11. }
  12.  
  13. class client : public QMainWindow
  14. {
  15.     Q_OBJECT
  16.  
  17. public:
  18.     explicit client(QWidget *parent = 0);
  19.     ~client();
  20.  
  21.  
  22. private slots:
  23.     void on_pushButton_clicked();
  24.  
  25. public slots:
  26.     void leer_socketserver();
  27.  
  28. private:
  29.     Ui::client *ui;
  30.  
  31.     QTcpSocket *tcpclient;
  32. };
  33.  
  34. #endif // CLIENT_H
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client.cpp
Qt Code: 
  1. #include "client.h"
  2. #include "ui_client.h"
  3.  
  4. client::client(QWidget *parent) :
  5.     QMainWindow(parent),
  6.     ui(new Ui::client)
  7. {
  8.     ui->setupUi(this);
  9.  
  10.     tcpclient = new QTcpSocket (this);
  11.  
  12.     tcpclient->connectToHost( QHostAddress::LocalHost , 1234);
  13.  
  14.     connect (tcpclient, SIGNAL (readyRead()), this, SLOT (leer_socketserver()));
  15. }
  16.  
  17. client::~client()
  18. {
  19.     delete ui;
  20. }
  21.  
  22. void client::on_pushButton_clicked()
  23. {
  24.     tcpclient->write( ui->lineEdit->text().toLatin1().data(), ui->lineEdit->text().size());
  25.     ui->lineEdit->clear();
  26. }
  27.  
  28. void client::leer_socketserver()
  29. {
  30.     QByteArray buffer;
  31.     buffer.resize( tcpclient->bytesAvailable() );
  32.     tcpclient->read( buffer.data(), buffer.size() );
  33.     ui->plainTextEdit->setReadOnly( true );
  34.     ui->plainTextEdit->appendPlainText( QString (buffer));
  35. }
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main.cpp
Qt Code: 
  1. #include "client.h"
  2. #include <QApplication>
  3.  
  4. int main(int argc, char *argv[])
  5. {
  6.     QApplication a(argc, argv);
  7.     client w;
  8.     w.show();
  9.  
  10.     return a.exec();
  11. }
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=========================
server.ui
Qt Code: 
  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <ui version="4.0">
  3.  <class>server</class>
  4.  <widget class="QMainWindow" name="server">
  5.   <property name="geometry">
  6.    <rect>
  7.     <x>0</x>
  8.     <y>0</y>
  9.     <width>376</width>
  10.     <height>335</height>
  11.    </rect>
  12.   </property>
  13.   <property name="windowTitle">
  14.    <string>server</string>
  15.   </property>
  16.   <widget class="QWidget" name="centralWidget">
  17.    <widget class="QLineEdit" name="lineEdit">
  18.     <property name="geometry">
  19.      <rect>
  20.       <x>100</x>
  21.       <y>200</y>
  22.       <width>261</width>
  23.       <height>20</height>
  24.      </rect>
  25.     </property>
  26.    </widget>
  27.    <widget class="QLabel" name="label">
  28.     <property name="geometry">
  29.      <rect>
  30.       <x>10</x>
  31.       <y>200</y>
  32.       <width>91</width>
  33.       <height>16</height>
  34.      </rect>
  35.     </property>
  36.     <property name="text">
  37.      <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>
  38.     </property>
  39.    </widget>
  40.    <widget class="QLabel" name="label_2">
  41.     <property name="geometry">
  42.      <rect>
  43.       <x>20</x>
  44.       <y>10</y>
  45.       <width>91</width>
  46.       <height>16</height>
  47.      </rect>
  48.     </property>
  49.     <property name="text">
  50.      <string>Chat</string>
  51.     </property>
  52.    </widget>
  53.    <widget class="QPushButton" name="pushButton">
  54.     <property name="geometry">
  55.      <rect>
  56.       <x>250</x>
  57.       <y>230</y>
  58.       <width>111</width>
  59.       <height>23</height>
  60.      </rect>
  61.     </property>
  62.     <property name="text">
  63.      <string>Wyslij na client</string>
  64.     </property>
  65.    </widget>
  66.    <widget class="QPlainTextEdit" name="plainTextEdit">
  67.     <property name="geometry">
  68.      <rect>
  69.       <x>20</x>
  70.       <y>30</y>
  71.       <width>341</width>
  72.       <height>151</height>
  73.      </rect>
  74.     </property>
  75.    </widget>
  76.   </widget>
  77.   <widget class="QMenuBar" name="menuBar">
  78.    <property name="geometry">
  79.     <rect>
  80.      <x>0</x>
  81.      <y>0</y>
  82.      <width>376</width>
  83.      <height>21</height>
  84.     </rect>
  85.    </property>
  86.   </widget>
  87.   <widget class="QToolBar" name="mainToolBar">
  88.    <attribute name="toolBarArea">
  89.     <enum>TopToolBarArea</enum>
  90.    </attribute>
  91.    <attribute name="toolBarBreak">
  92.     <bool>false</bool>
  93.    </attribute>
  94.   </widget>
  95.   <widget class="QStatusBar" name="statusBar"/>
  96.  </widget>
  97.  <layoutdefault spacing="6" margin="11"/>
  98.  <resources/>
  99.  <connections/>
  100. </ui>
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