Qt 5.11 | Qt Network | Network Chat Example | connection.cpp Example File

Qt 5.11.3 Reference Documentation

# connection.cpp Example File

network-chat/connection.cpp

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      #include "connection.h"

      #include <QtNetwork>

      static const int TransferTimeout = 30 * 1000;
      static const int PongTimeout = 60 * 1000;
      static const int PingInterval = 5 * 1000;
      static const char SeparatorToken = ' ';

      Connection::Connection(QObject *parent)
          : QTcpSocket(parent)
      {
          greetingMessage = tr("undefined");
          username = tr("unknown");
          state = WaitingForGreeting;
          currentDataType = Undefined;
          numBytesForCurrentDataType = -1;
          transferTimerId = 0;
          isGreetingMessageSent = false;
          pingTimer.setInterval(PingInterval);

          QObject::connect(this, SIGNAL(readyRead()), this, SLOT(processReadyRead()));
          QObject::connect(this, SIGNAL(disconnected()), &pingTimer, SLOT(stop()));
          QObject::connect(&pingTimer, SIGNAL(timeout()), this, SLOT(sendPing()));
          QObject::connect(this, SIGNAL(connected()),
                           this, SLOT(sendGreetingMessage()));
      }

      QString Connection::name() const
      {
          return username;
      }

      void Connection::setGreetingMessage(const QString &message)
      {
          greetingMessage = message;
      }

      bool Connection::sendMessage(const QString &message)
      {
          if (message.isEmpty())
              return false;

          QByteArray msg = message.toUtf8();
          QByteArray data = "MESSAGE " + QByteArray::number(msg.size()) + ' ' + msg;
          return write(data) == data.size();
      }

      void Connection::timerEvent(QTimerEvent *timerEvent)
      {
          if (timerEvent->timerId() == transferTimerId) {
              abort();
              killTimer(transferTimerId);
              transferTimerId = 0;
          }
      }

      void Connection::processReadyRead()
      {
          if (state == WaitingForGreeting) {
              if (!readProtocolHeader())
                  return;
              if (currentDataType != Greeting) {
                  abort();
                  return;
              }
              state = ReadingGreeting;
          }

          if (state == ReadingGreeting) {
              if (!hasEnoughData())
                  return;

              buffer = read(numBytesForCurrentDataType);
              if (buffer.size() != numBytesForCurrentDataType) {
                  abort();
                  return;
              }

              username = QString(buffer) + '@' + peerAddress().toString() + ':'
                         + QString::number(peerPort());
              currentDataType = Undefined;
              numBytesForCurrentDataType = 0;
              buffer.clear();

              if (!isValid()) {
                  abort();
                  return;
              }

              if (!isGreetingMessageSent)
                  sendGreetingMessage();

              pingTimer.start();
              pongTime.start();
              state = ReadyForUse;
              emit readyForUse();
          }

          do {
              if (currentDataType == Undefined) {
                  if (!readProtocolHeader())
                      return;
              }
              if (!hasEnoughData())
                  return;
              processData();
          } while (bytesAvailable() > 0);
      }

      void Connection::sendPing()
      {
          if (pongTime.elapsed() > PongTimeout) {
              abort();
              return;
          }

          write("PING 1 p");
      }

      void Connection::sendGreetingMessage()
      {
          QByteArray greeting = greetingMessage.toUtf8();
          QByteArray data = "GREETING " + QByteArray::number(greeting.size()) + ' ' + greeting;
          if (write(data) == data.size())
              isGreetingMessageSent = true;
      }

      int Connection::readDataIntoBuffer(int maxSize)
      {
          if (maxSize > MaxBufferSize)
              return 0;

          int numBytesBeforeRead = buffer.size();
          if (numBytesBeforeRead == MaxBufferSize) {
              abort();
              return 0;
          }

          while (bytesAvailable() > 0 && buffer.size() < maxSize) {
              buffer.append(read(1));
              if (buffer.endsWith(SeparatorToken))
                  break;
          }
          return buffer.size() - numBytesBeforeRead;
      }

      int Connection::dataLengthForCurrentDataType()
      {
          if (bytesAvailable() <= 0 || readDataIntoBuffer() <= 0
                  || !buffer.endsWith(SeparatorToken))
              return 0;

          buffer.chop(1);
          int number = buffer.toInt();
          buffer.clear();
          return number;
      }

      bool Connection::readProtocolHeader()
      {
          if (transferTimerId) {
              killTimer(transferTimerId);
              transferTimerId = 0;
          }

          if (readDataIntoBuffer() <= 0) {
              transferTimerId = startTimer(TransferTimeout);
              return false;
          }

          if (buffer == "PING ") {
              currentDataType = Ping;
          } else if (buffer == "PONG ") {
              currentDataType = Pong;
          } else if (buffer == "MESSAGE ") {
              currentDataType = PlainText;
          } else if (buffer == "GREETING ") {
              currentDataType = Greeting;
          } else {
              currentDataType = Undefined;
              abort();
              return false;
          }

          buffer.clear();
          numBytesForCurrentDataType = dataLengthForCurrentDataType();
          return true;
      }

      bool Connection::hasEnoughData()
      {
          if (transferTimerId) {
              QObject::killTimer(transferTimerId);
              transferTimerId = 0;
          }

          if (numBytesForCurrentDataType <= 0)
              numBytesForCurrentDataType = dataLengthForCurrentDataType();

          if (bytesAvailable() < numBytesForCurrentDataType
                  || numBytesForCurrentDataType <= 0) {
              transferTimerId = startTimer(TransferTimeout);
              return false;
          }

          return true;
      }

      void Connection::processData()
      {
          buffer = read(numBytesForCurrentDataType);
          if (buffer.size() != numBytesForCurrentDataType) {
              abort();
              return;
          }

          switch (currentDataType) {
          case PlainText:
              emit newMessage(username, QString::fromUtf8(buffer));
              break;
          case Ping:
              write("PONG 1 p");
              break;
          case Pong:
              pongTime.restart();
              break;
          default:
              break;
          }

          currentDataType = Undefined;
          numBytesForCurrentDataType = 0;
          buffer.clear();
      }