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;

  /*
   * Protocol is defined as follows, using the CBOR Data Definition Language:
   *
   *  protocol    = [
   *     greeting,        ; must start with a greeting command
   *     * command        ; zero or more regular commands after
   *  ]
   *  command     = plaintext / ping / pong / greeting
   *  plaintext   = { 0 => text }
   *  ping        = { 1 => null }
   *  pong        = { 2 => null }
   *  greeting    = { 3 => text }
   */

  Connection::Connection(QObject *parent)
      : QTcpSocket(parent), writer(this)
  {
      greetingMessage = tr("undefined");
      username = tr("unknown");
      state = WaitingForGreeting;
      currentDataType = Undefined;
      transferTimerId = -1;
      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()));
  }

  Connection::Connection(qintptr socketDescriptor, QObject *parent)
      : Connection(parent)
  {
      setSocketDescriptor(socketDescriptor);
      reader.setDevice(this);
  }

  Connection::~Connection()
  {
      if (isGreetingMessageSent) {
          // Indicate clean shutdown.
          writer.endArray();
          waitForBytesWritten(2000);
      }
  }

  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;

      writer.startMap(1);
      writer.append(PlainText);
      writer.append(message);
      writer.endMap();
      return true;
  }

  void Connection::timerEvent(QTimerEvent *timerEvent)
  {
      if (timerEvent->timerId() == transferTimerId) {
          abort();
          killTimer(transferTimerId);
          transferTimerId = -1;
      }
  }

  void Connection::processReadyRead()
  {
      // we've got more data, let's parse
      reader.reparse();
      while (reader.lastError() == QCborError::NoError) {
          if (state == WaitingForGreeting) {
              if (!reader.isArray())
                  break;                  // protocol error

              reader.enterContainer();    // we'll be in this array forever
              state = ReadingGreeting;
          } else if (reader.containerDepth() == 1) {
              // Current state: no command read
              // Next state: read command ID
              if (!reader.hasNext()) {
                  reader.leaveContainer();
                  disconnectFromHost();
                  return;
              }

              if (!reader.isMap() || !reader.isLengthKnown() || reader.length() != 1)
                  break;                  // protocol error
              reader.enterContainer();
          } else if (currentDataType == Undefined) {
              // Current state: read command ID
              // Next state: read command payload
              if (!reader.isInteger())
                  break;                  // protocol error
              currentDataType = DataType(reader.toInteger());
              reader.next();
          } else {
              // Current state: read command payload
              if (reader.isString()) {
                  auto r = reader.readString();
                  buffer += r.data;
                  if (r.status != QCborStreamReader::EndOfString)
                      continue;
              } else if (reader.isNull()) {
                  reader.next();
              } else {
                  break;                   // protocol error
              }

              // Next state: no command read
              reader.leaveContainer();
              if (transferTimerId != -1) {
                  killTimer(transferTimerId);
                  transferTimerId = -1;
              }

              if (state == ReadingGreeting) {
                  if (currentDataType != Greeting)
                      break;              // protocol error
                  processGreeting();
              } else {
                  processData();
              }
          }
      }

      if (reader.lastError() != QCborError::EndOfFile)
          abort();       // parse error

      if (transferTimerId != -1 && reader.containerDepth() > 1)
          transferTimerId = startTimer(TransferTimeout);
  }

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

      writer.startMap(1);
      writer.append(Ping);
      writer.append(nullptr);     // no payload
      writer.endMap();
  }

  void Connection::sendGreetingMessage()
  {
      writer.startArray();        // this array never ends

      writer.startMap(1);
      writer.append(Greeting);
      writer.append(greetingMessage);
      writer.endMap();
      isGreetingMessageSent = true;

      if (!reader.device())
          reader.setDevice(this);
  }

  void Connection::processGreeting()
  {
      username = buffer + '@' + peerAddress().toString() + ':'
              + QString::number(peerPort());
      currentDataType = Undefined;
      buffer.clear();

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

      if (!isGreetingMessageSent)
          sendGreetingMessage();

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

  void Connection::processData()
  {
      switch (currentDataType) {
      case PlainText:
          emit newMessage(username, buffer);
          break;
      case Ping:
          writer.startMap(1);
          writer.append(Pong);
          writer.append(nullptr);     // no payload
          writer.endMap();
          break;
      case Pong:
          pongTime.restart();
          break;
      default:
          break;
      }

      currentDataType = Undefined;
      buffer.clear();
  }