connection.h Example File
network/network-chat/connection.h

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 #ifndef CONNECTION_H
 #define CONNECTION_H

 #include <QHostAddress>
 #include <QString>
 #include <QTcpSocket>
 #include <QTime>
 #include <QTimer>

 static const int MaxBufferSize = 1024000;

 class Connection : public QTcpSocket
 {
     Q_OBJECT

 public:
     enum ConnectionState {
         WaitingForGreeting,
         ReadingGreeting,
         ReadyForUse
     };
     enum DataType {
         PlainText,
         Ping,
         Pong,
         Greeting,
         Undefined
     };

     Connection(QObject *parent = 0);

     QString name() const;
     void setGreetingMessage(const QString &message);
     bool sendMessage(const QString &message);

 signals:
     void readyForUse();
     void newMessage(const QString &from, const QString &message);

 protected:
     void timerEvent(QTimerEvent *timerEvent);

 private slots:
     void processReadyRead();
     void sendPing();
     void sendGreetingMessage();

 private:
     int readDataIntoBuffer(int maxSize = MaxBufferSize);
     int dataLengthForCurrentDataType();
     bool readProtocolHeader();
     bool hasEnoughData();
     void processData();

     QString greetingMessage;
     QString username;
     QTimer pingTimer;
     QTime pongTime;
     QByteArray buffer;
     ConnectionState state;
     DataType currentDataType;
     int numBytesForCurrentDataType;
     int transferTimerId;
     bool isGreetingMessageSent;
 };

 #endif