diff --git a/src/mqtt/qmqtt_client.cpp b/src/mqtt/qmqtt_client.cpp
index 6a07d9d..f46457f 100644
--- a/src/mqtt/qmqtt_client.cpp
+++ b/src/mqtt/qmqtt_client.cpp
@@ -155,13 +155,13 @@ void QMQTT::Client::setVersion(const QMQTT::MQTTVersion version)
     d->setVersion(version);
 }
 
-QString QMQTT::Client::password() const
+QByteArray QMQTT::Client::password() const
 {
     Q_D(const Client);
     return d->password();
 }
 
-void QMQTT::Client::setPassword(const QString& password)
+void QMQTT::Client::setPassword(const QByteArray &password)
 {
     Q_D(Client);
     d->setPassword(password);
@@ -251,13 +251,13 @@ void QMQTT::Client::setWillRetain(const bool willRetain)
     d->setWillRetain(willRetain);
 }
 
-QString QMQTT::Client::willMessage() const
+QByteArray QMQTT::Client::willMessage() const
 {
     Q_D(const Client);
     return d->willMessage();
 }
 
-void QMQTT::Client::setWillMessage(const QString& willMessage)
+void QMQTT::Client::setWillMessage(const QByteArray &willMessage)
 {
     Q_D(Client);
     d->setWillMessage(willMessage);
diff --git a/src/mqtt/qmqtt_client.h b/src/mqtt/qmqtt_client.h
index dec14da..fae948a 100644
--- a/src/mqtt/qmqtt_client.h
+++ b/src/mqtt/qmqtt_client.h
@@ -105,7 +105,7 @@ class Q_MQTT_EXPORT Client : public QObject
     Q_PROPERTY(QString _hostName READ hostName WRITE setHostName)
     Q_PROPERTY(QString _clientId READ clientId WRITE setClientId)
     Q_PROPERTY(QString _username READ username WRITE setUsername)
-    Q_PROPERTY(QString _password READ password WRITE setPassword)
+    Q_PROPERTY(QByteArray _password READ password WRITE setPassword)
     Q_PROPERTY(quint16 _keepAlive READ keepAlive WRITE setKeepAlive)
     Q_PROPERTY(MQTTVersion _version READ version WRITE setVersion)
     Q_PROPERTY(bool _autoReconnect READ autoReconnect WRITE setAutoReconnect)
@@ -114,7 +114,7 @@ class Q_MQTT_EXPORT Client : public QObject
     Q_PROPERTY(QString _willTopic READ willTopic WRITE setWillTopic)
     Q_PROPERTY(quint8 _willQos READ willQos WRITE setWillQos)
     Q_PROPERTY(bool _willRetain READ willRetain WRITE setWillRetain)
-    Q_PROPERTY(QString _willMessage READ willMessage WRITE setWillMessage)
+    Q_PROPERTY(QByteArray _willMessage READ willMessage WRITE setWillMessage)
     Q_PROPERTY(QString _connectionState READ connectionState)
 
 public:
@@ -153,7 +153,7 @@ class Q_MQTT_EXPORT Client : public QObject
     quint16 port() const;
     QString clientId() const;
     QString username() const;
-    QString password() const;
+    QByteArray password() const;
     QMQTT::MQTTVersion version() const;
     quint16 keepAlive() const;
     bool cleanSession() const;
@@ -163,7 +163,7 @@ class Q_MQTT_EXPORT Client : public QObject
     QString willTopic() const;
     quint8 willQos() const;
     bool willRetain() const;
-    QString willMessage() const;
+    QByteArray willMessage() const;
 
     bool isConnectedToHost() const;
 
@@ -173,7 +173,7 @@ public slots:
     void setPort(const quint16 port);
     void setClientId(const QString& clientId);
     void setUsername(const QString& username);
-    void setPassword(const QString& password);
+    void setPassword(const QByteArray& password);
     void setVersion(const MQTTVersion version);
     void setKeepAlive(const quint16 keepAlive);
     void setCleanSession(const bool cleanSession);
@@ -182,7 +182,7 @@ public slots:
     void setWillTopic(const QString& willTopic);
     void setWillQos(const quint8 willQos);
     void setWillRetain(const bool willRetain);
-    void setWillMessage(const QString& willMessage);
+    void setWillMessage(const QByteArray& willMessage);
 
     void connectToHost();
     void disconnectFromHost();
diff --git a/src/mqtt/qmqtt_client_p.cpp b/src/mqtt/qmqtt_client_p.cpp
index 9a08012..c17811e 100644
--- a/src/mqtt/qmqtt_client_p.cpp
+++ b/src/mqtt/qmqtt_client_p.cpp
@@ -222,7 +222,7 @@ void QMQTT::ClientPrivate::sendConnect()
         frame.writeString(willTopic());
         if(!willMessage().isEmpty())
         {
-            frame.writeString(willMessage());
+            frame.writeByteArray(_willMessage);
         }
     }
     if (!_username.isEmpty())
@@ -230,7 +230,7 @@ void QMQTT::ClientPrivate::sendConnect()
         frame.writeString(_username);
         if (!_password.isEmpty())
         {
-            frame.writeString(_password);
+            frame.writeByteArray(_password);
         }
     }
     _network->sendFrame(frame);
@@ -543,12 +543,12 @@ quint16 QMQTT::ClientPrivate::keepAlive() const
     return _keepAlive;
 }
 
-void QMQTT::ClientPrivate::setPassword(const QString& password)
+void QMQTT::ClientPrivate::setPassword(const QByteArray& password)
 {
     _password = password;
 }
 
-QString QMQTT::ClientPrivate::password() const
+QByteArray QMQTT::ClientPrivate::password() const
 {
     return _password;
 }
@@ -650,12 +650,12 @@ void QMQTT::ClientPrivate::setWillRetain(const bool willRetain)
     _willRetain = willRetain;
 }
 
-QString QMQTT::ClientPrivate::willMessage() const
+QByteArray QMQTT::ClientPrivate::willMessage() const
 {
     return _willMessage;
 }
 
-void QMQTT::ClientPrivate::setWillMessage(const QString& willMessage)
+void QMQTT::ClientPrivate::setWillMessage(const QByteArray& willMessage)
 {
     _willMessage = willMessage;
 }
diff --git a/src/mqtt/qmqtt_client_p.h b/src/mqtt/qmqtt_client_p.h
index fcffdcc..fbf9a52 100644
--- a/src/mqtt/qmqtt_client_p.h
+++ b/src/mqtt/qmqtt_client_p.h
@@ -64,7 +64,7 @@ class ClientPrivate
     MQTTVersion _version;
     QString _clientId;
     QString _username;
-    QString _password;
+    QByteArray _password;
     bool _cleanSession;
     quint16 _keepAlive;
     ConnectionState _connectionState;
@@ -73,7 +73,7 @@ class ClientPrivate
     QString _willTopic;
     quint8 _willQos;
     bool _willRetain;
-    QString _willMessage;
+    QByteArray _willMessage;
     QHash<QAbstractSocket::SocketError, ClientError> _socketErrorHash;
     QHash<quint16, QString> _midToTopic;
 
@@ -117,8 +117,8 @@ class ClientPrivate
     bool cleanSession() const;
     void setKeepAlive(const quint16 keepAlive);
     quint16 keepAlive() const;
-    void setPassword(const QString& password);
-    QString password() const;
+    void setPassword(const QByteArray& password);
+    QByteArray password() const;
     void setUsername(const QString& username);
     QString username() const;
     void setVersion(const MQTTVersion);
@@ -134,11 +134,11 @@ class ClientPrivate
     void setWillTopic(const QString& willTopic);
     void setWillQos(const quint8 willQos);
     void setWillRetain(const bool willRetain);
-    void setWillMessage(const QString& willMessage);
+    void setWillMessage(const QByteArray& willMessage);
     QString willTopic() const;
     quint8 willQos() const;
     bool willRetain() const;
-    QString willMessage() const;
+    QByteArray willMessage() const;
     void initializeErrorHash();
     void onNetworkError(QAbstractSocket::SocketError error);
 
diff --git a/src/mqtt/qmqtt_frame.cpp b/src/mqtt/qmqtt_frame.cpp
index be8576c..6791859 100644
--- a/src/mqtt/qmqtt_frame.cpp
+++ b/src/mqtt/qmqtt_frame.cpp
@@ -104,6 +104,14 @@ quint16 Frame::readInt()
     return (msb << 8) | lsb;
 }
 
+QByteArray Frame::readByteArray()
+{
+    quint16 len = readInt();
+    QByteArray data = _data.left(len);
+    _data.remove(0, len);
+    return data;
+}
+
 QString Frame::readString()
 {
     quint16 len = readInt();
@@ -118,6 +126,20 @@ void Frame::writeInt(const quint16 i)
     _data.append(LSB(i));
 }
 
+void Frame::writeByteArray(const QByteArray &data)
+{
+    if (data.size() > (int)USHRT_MAX)
+    {
+        qCritical("qmqtt: Binary data size bigger than %u bytes, truncate it!", USHRT_MAX);
+        writeInt(USHRT_MAX);
+        _data.append(data.left(USHRT_MAX));
+        return;
+    }
+
+    writeInt(data.size());
+    _data.append(data);
+}
+
 void Frame::writeString(const QString &string)
 {
     QByteArray data = string.toUtf8();
diff --git a/src/mqtt/qmqtt_frame.h b/src/mqtt/qmqtt_frame.h
index 15e27dc..5cca7fb 100644
--- a/src/mqtt/qmqtt_frame.h
+++ b/src/mqtt/qmqtt_frame.h
@@ -106,10 +106,12 @@ class Q_MQTT_EXPORT Frame
 
     quint16 readInt();
     quint8 readChar();
+    QByteArray readByteArray();
     QString readString();
 
     void writeInt(const quint16 i);
     void writeChar(const quint8 c);
+    void writeByteArray(const QByteArray &data);
     void writeString(const QString &string);
     void writeRawData(const QByteArray &data);