diff --git a/data/settingshandler.cpp b/data/settingshandler.cpp
index eb11006..691854b 100644
--- a/data/settingshandler.cpp
+++ b/data/settingshandler.cpp
@@ -40,4 +40,48 @@ void SettingsHandler::saveSettings(QVariantMap settingMap, QString group) {
   settings.sync();
 }
 
+void SettingsHandler::deleteSettings(QStringList keys, QString group) {
+  qInfo() << "deleting settings...";
+
+  QSettings settings;
+  if (!group.isEmpty()) {
+    qDebug() << "starting group:" << group;
+    settings.beginGroup(group);
+  }
+
+  foreach (QString key, keys) {
+    qDebug() << "removing:" << key;
+    settings.remove(key);
+  }
+  if (!group.isEmpty()) {
+    settings.endGroup();
+  }
+
+  settings.sync();
+}
+
+QVariantMap SettingsHandler::getChangeset(QVariantMap newSettings, QString group) {
+  const QVariantMap oldSettings = getSettings(group);
+
+  QVariantMap result;
+
+  for (QVariantMap::const_iterator iter = newSettings.begin(); iter != newSettings.end(); ++iter) {
+    qDebug() << iter.key() << iter.value();
+    QString key       = iter.key();
+    QVariant newValue = iter.value();
+    QVariant oldValue = oldSettings.value(key);
+
+    if (oldValue == newValue) {
+      qInfo() << "oldValue == newValue -> ignoring...";
+    } else {
+      const QString debugString =
+          QString("oldValue != newValue -> adding '%1' to changeset...").arg(key);
+      qInfo() << debugString;
+      result.insert(key, newValue);
+    }
+  }
+
+  return result;
+}
+
 SettingsHandler::SettingsHandler() {}
diff --git a/data/settingshandler.h b/data/settingshandler.h
index a636cf6..3488939 100644
--- a/data/settingshandler.h
+++ b/data/settingshandler.h
@@ -7,6 +7,9 @@ class SettingsHandler {
  public:
   static QVariantMap getSettings(QString group = "");
   static void saveSettings(QVariantMap settingMap, QString group = "");
+  static void deleteSettings(QStringList keys, QString group = "");
+
+  static QVariantMap getChangeset(QVariantMap newSettings, QString group = "");
 
  private:
   SettingsHandler();
diff --git a/formats/jsonparser.cpp b/formats/jsonparser.cpp
index 559ea20..b41c1e2 100644
--- a/formats/jsonparser.cpp
+++ b/formats/jsonparser.cpp
@@ -74,6 +74,30 @@ QJsonObject JsonParser::itemValuesToJsonObject(const ModelItemValues& itemValues
   return result;
 }
 
+QByteArray JsonParser::userCredentialsToJsonDocument(const QString email, const QString password) {
+  QJsonDocument jsonDoc;
+  QJsonObject rootObject;
+
+  QJsonObject userObject;
+  userObject.insert("email", email);
+  userObject.insert("password", password);
+
+  rootObject.insert("user", userObject);
+  jsonDoc.setObject(rootObject);
+
+  return jsonDoc.toJson(QJsonDocument::Compact);
+}
+
+QVariant JsonParser::getValueFromJson(const QByteArray& jsonData,
+                                      const QString key,
+                                      const QString objectName) {
+  QJsonDocument doc      = QJsonDocument::fromJson(jsonData);
+  QJsonObject rootObject = doc.object();
+  QJsonObject userObject = rootObject.value(objectName).toObject();
+
+  return userObject.value(key);
+}
+
 JsonParser::JsonParser() {}
 
 QJsonArray JsonParser::extractItemArray(const QJsonDocument& doc, const QString& objectName) {
diff --git a/formats/jsonparser.h b/formats/jsonparser.h
index ba2a95f..fa805af 100644
--- a/formats/jsonparser.h
+++ b/formats/jsonparser.h
@@ -20,6 +20,11 @@ class JsonParser {
                                          const QString& objectName = "");
   static QJsonObject itemValuesToJsonObject(const ModelItemValues& itemValues);
 
+  static QByteArray userCredentialsToJsonDocument(const QString email, const QString password);
+  static QVariant getValueFromJson(const QByteArray& jsonData,
+                                   const QString key,
+                                   const QString objectName = "");
+
  private:
   explicit JsonParser();
 
diff --git a/genericcore.cpp b/genericcore.cpp
index c21c655..c5d7f76 100644
--- a/genericcore.cpp
+++ b/genericcore.cpp
@@ -14,6 +14,7 @@
 #include "constants.h"
 #include "data/filehandler.h"
 #include "data/settingshandler.h"
+#include "formats/jsonparser.h"
 #include "model/generalsortfiltermodel.h"
 #include "model/metadata.h"
 #include "model/tablemodel.h"
@@ -126,6 +127,24 @@ QVariantMap GenericCore::getSettings(QString group) const {
 }
 
 void GenericCore::applySettings(QVariantMap settingMap, QString group) {
+  const QVariantMap changeset = SettingsHandler::getChangeset(settingMap, group);
+
+  if (changeset.isEmpty()) {
+    return;
+  }
+
+  if (group == "Server") {
+    const bool urlChanged      = changeset.contains("url");
+    const bool emailChanged    = changeset.contains("email");
+    const bool passwordChanged = changeset.contains("password");
+    if (urlChanged || emailChanged || passwordChanged) {
+      if (!changeset.contains("authToken")) {
+        qInfo() << "Account settings changed, but no new token present. Deleting old token...";
+        SettingsHandler::deleteSettings({"authToken"}, "Server");
+      }
+    }
+  }
+
   SettingsHandler::saveSettings(settingMap, group);
 
   if (group == "Server") {
@@ -158,8 +177,32 @@ void GenericCore::saveItems() {
   }
 }
 
+void GenericCore::onLoginSuccessful(const QByteArray jsonData) {
+  emit displayStatusMessage("Login successful.");
+  qInfo() << "Storing auth token...";
+  QString token = JsonParser::getValueFromJson(jsonData, "token", "user").toString();
+  SettingsHandler::saveSettings({{"authToken", token}}, "Server");
+  applyServerConfiguration();
+}
+
+void GenericCore::onLoginFailure(const QString errorString) {
+  emit displayStatusMessage(QString("Error: %1").arg(errorString));
+}
+
+void GenericCore::onNotAuthorized(const QString /*path*/) {
+  const QVariantMap serverSettings = SettingsHandler::getSettings("Server");
+  const QString tokenValue         = serverSettings.value("authToken").toString();
+  if (!tokenValue.isEmpty()) {
+    SettingsHandler::deleteSettings({"authToken"}, "Server");
+    displayStatusMessage("Not authorized! Deleted token. Please retry.");
+  } else {
+    displayStatusMessage("Not authorized! But no token was present. Please check your settings.");
+  }
+  applyServerConfiguration();
+}
+
 void GenericCore::onSendItemTriggered(const QByteArray& jsonData) {
-  m_serverCommunicator->postItems(jsonData);
+  m_serverCommunicator->sendItem(jsonData);
 }
 
 void GenericCore::onItemsFetched(const QByteArray jsonData) {
@@ -173,20 +216,20 @@ void GenericCore::onItemsFetchFailure(const QString errorString) {
   emit displayStatusMessage(QString("Error: %1").arg(errorString));
 }
 
-void GenericCore::onPostRequestSuccessful(const QByteArray responseData) {
+void GenericCore::onSendItemSuccessful(const QByteArray responseData) {
   const QString message = m_mainModel->updateItemsFromJson(responseData);
   emit displayStatusMessage(message);
 }
 
-void GenericCore::onPostRequestFailure(const QString errorString) {
+void GenericCore::onSendItemFailure(const QString errorString) {
   emit displayStatusMessage(QString("Error: %1").arg(errorString));
 }
 
-void GenericCore::onDeleteRequestSuccessful(const QByteArray responseData) {
+void GenericCore::onDeleteItemSuccessful(const QByteArray responseData) {
   qWarning() << "TODO: Process success response!!!";
 }
 
-void GenericCore::onDeleteRequestFailure(const QString errorString) {
+void GenericCore::onDeleteItemFailure(const QString errorString) {
   qWarning() << "TODO: Process error response!!!";
 }
 
@@ -252,23 +295,32 @@ void GenericCore::setupServerCommunication() {
   /// request connections
   connect(this, &GenericCore::fetchItemsFromServer, m_serverCommunicator.get(),
           &ServerCommunicator::fetchItems);
-  connect(this, &GenericCore::postItemToServer, this, &GenericCore::onSendItemTriggered);
+  connect(this, &GenericCore::sendItemToServer, m_serverCommunicator.get(),
+          &ServerCommunicator::sendItem);
   connect(this, &GenericCore::deleteItemFromServer, m_serverCommunicator.get(),
           &ServerCommunicator::deleteItem);
 
   /// response connections
+  connect(m_serverCommunicator.get(), &ServerCommunicator::loginSuccessful, this,
+          &GenericCore::onLoginSuccessful);
+  connect(m_serverCommunicator.get(), &ServerCommunicator::loginFailure, this,
+          &GenericCore::onLoginFailure);
+
+  connect(m_serverCommunicator.get(), &ServerCommunicator::notAuthorized, this,
+          &GenericCore::onNotAuthorized);
+
   connect(m_serverCommunicator.get(), &ServerCommunicator::itemsFetched, this,
           &GenericCore::onItemsFetched);
   connect(m_serverCommunicator.get(), &ServerCommunicator::itemsFetchFailure, this,
           &GenericCore::onItemsFetchFailure);
-  connect(m_serverCommunicator.get(), &ServerCommunicator::postRequestSuccessful, this,
-          &GenericCore::onPostRequestSuccessful);
-  connect(m_serverCommunicator.get(), &ServerCommunicator::postRequestFailure, this,
-          &GenericCore::onPostRequestFailure);
-  connect(m_serverCommunicator.get(), &ServerCommunicator::deleteRequestSuccessful, this,
-          &GenericCore::onDeleteRequestSuccessful);
-  connect(m_serverCommunicator.get(), &ServerCommunicator::deleteRequestFailure, this,
-          &GenericCore::onDeleteRequestFailure);
+  connect(m_serverCommunicator.get(), &ServerCommunicator::sendItemSuccessful, this,
+          &GenericCore::onSendItemSuccessful);
+  connect(m_serverCommunicator.get(), &ServerCommunicator::sendItemFailure, this,
+          &GenericCore::onSendItemFailure);
+  connect(m_serverCommunicator.get(), &ServerCommunicator::deleteItemSuccessful, this,
+          &GenericCore::onDeleteItemSuccessful);
+  connect(m_serverCommunicator.get(), &ServerCommunicator::deleteItemFailure, this,
+          &GenericCore::onDeleteItemFailure);
 
   applyServerConfiguration();
 }
@@ -276,8 +328,10 @@ void GenericCore::setupServerCommunication() {
 void GenericCore::applyServerConfiguration() {
   const QVariantMap serverSettings = SettingsHandler::getSettings("Server");
   const QString urlValue           = serverSettings.value("url").toString();
-  // NEXT if urlValue is empty -> remove authToken from settings?
-  if (!urlValue.isEmpty()) {
+  if (urlValue.isEmpty()) {
+    SettingsHandler::deleteSettings({"authToken"}, "Server");
+  } else {
+    /// urlValue in NOT empty
     const QString emailValue     = serverSettings.value("email").toString();
     const QString passwordValue  = serverSettings.value("password").toString();
     const QString authTokenValue = serverSettings.value("authToken").toString();
diff --git a/genericcore.h b/genericcore.h
index 722b5cd..22df81a 100644
--- a/genericcore.h
+++ b/genericcore.h
@@ -39,18 +39,23 @@ class GenericCore : public QObject {
  public slots:
   void saveItems();
 
+  void onLoginSuccessful(const QByteArray jsonData);
+  void onLoginFailure(const QString errorString);
+
+  void onNotAuthorized(const QString /*path*/);
+
   void onSendItemTriggered(const QByteArray& jsonData);
   void onItemsFetched(const QByteArray jsonData);
   void onItemsFetchFailure(const QString errorString);
-  void onPostRequestSuccessful(const QByteArray responseData);
-  void onPostRequestFailure(const QString errorString);
-  void onDeleteRequestSuccessful(const QByteArray responseData);
-  void onDeleteRequestFailure(const QString errorString);
+  void onSendItemSuccessful(const QByteArray responseData);
+  void onSendItemFailure(const QString errorString);
+  void onDeleteItemSuccessful(const QByteArray responseData);
+  void onDeleteItemFailure(const QString errorString);
 
  signals:
   void displayStatusMessage(QString message);
   void fetchItemsFromServer();
-  void postItemToServer(const QByteArray& jsonData);
+  void sendItemToServer(const QByteArray& jsonData);
   void deleteItemFromServer(const QString& id);
 
  private:
diff --git a/network/apiroutes.h b/network/apiroutes.h
index e89da3a..12b25d6 100644
--- a/network/apiroutes.h
+++ b/network/apiroutes.h
@@ -7,6 +7,8 @@
 
 static const QString apiPrefix = "/api/";
 
+static const QString ROUTE_LOG_IN = apiPrefix + "log_in";
+
 static const QString ROUTE_ITEMS = apiPrefix + "items";
 
 #endif  // APIROUTES_H
diff --git a/network/servercommunicator.cpp b/network/servercommunicator.cpp
index 8b683a2..1684bf1 100644
--- a/network/servercommunicator.cpp
+++ b/network/servercommunicator.cpp
@@ -6,6 +6,8 @@
 #include <QJsonObject>
 #include <QRestReply>
 
+#include "../formats/jsonparser.h"
+
 using namespace Qt::StringLiterals;
 
 ServerCommunicator::ServerCommunicator(QObject* parent)
@@ -46,67 +48,176 @@ void ServerCommunicator::setServerConfiguration(const QString url,
   m_password  = password;
   m_authToken = authToken;
 
-  if (!authToken.isEmpty()) {
+  if (authToken.isEmpty()) {
+    if (validLoginCredentials()) {
+      const QByteArray userCredentials =
+          JsonParser::userCredentialsToJsonDocument(m_email, m_password);
+      sendPostRequest(ROUTE_LOG_IN, userCredentials);
+    }
+  } else {
+    /// authToken not empty:
     m_serviceApi->setBearerToken(authToken.toLatin1());
   }
 }
 
-void ServerCommunicator::fetchItems() {
-  /// Set up a GET request
-  m_restManager->get(m_serviceApi->createRequest(ROUTE_ITEMS), this, [this](QRestReply& reply) {
-    if (reply.isSuccess()) {
-      qInfo() << "Fetching items successful.";
-      const QJsonDocument doc = reply.readJson().value();
-      emit itemsFetched(doc.toJson());
+void ServerCommunicator::fetchItems() { sendGetRequest(ROUTE_ITEMS); }
 
+void ServerCommunicator::sendItem(const QByteArray& jsonData) {
+  sendPostRequest(ROUTE_ITEMS, jsonData);
+}
+
+void ServerCommunicator::deleteItem(const QString& id) {
+  const QString path = QString("%1/%2").arg(ROUTE_ITEMS, id);
+  sendDeleteRequest(path);
+}
+
+bool ServerCommunicator::validLoginCredentials() {
+  if (url().isEmpty()) {
+    return false;
+  }
+  if (m_email.isEmpty()) {
+    return false;
+  }
+  if (m_password.isEmpty()) {
+    return false;
+  }
+  return true;
+}
+
+void ServerCommunicator::sendGetRequest(const QString& path) {
+  // TODO check for valid path, instead of emptiness
+  if (path.isEmpty()) {
+    qDebug() << "Empty path -> Not sending a request.";
+    return;
+  }
+
+  const QNetworkRequest request = m_serviceApi->createRequest(path);
+  m_restManager->get(request, this, [this, path](QRestReply& reply) {
+    if (reply.isSuccess()) {
+      qInfo() << "Request successful.";
+      const QJsonDocument doc = reply.readJson().value();
+      onGetReplySuccessful(path, doc);
     } else {
       if (reply.hasError()) {
         const QString errorString = reply.errorString();
-        qCritical() << "ERROR:" << errorString;
-        emit itemsFetchFailure(errorString);
+        qWarning() << "Network error:" << errorString;
+        onGetReplyFailure(path, errorString);
       } else {
         int statusCode = reply.httpStatus();
-        qCritical() << "ERROR:" << statusCode;
-        emit itemsFetchFailure(QString::number(statusCode));
-        emit itemsFetchFailure(QString("HTTP status code: %1").arg(statusCode));
+        qWarning() << "Request not successful:" << statusCode;
+        if (statusCode == 401) {
+          notAuthorized(path);
+        } else {
+          onGetReplyFailure(path, QString("HTTP status code: %1").arg(statusCode));
+        }
       }
     }
   });
 }
 
-void ServerCommunicator::postItems(const QByteArray& jsonData) {
-  QNetworkReply* reply = m_restManager->post(m_serviceApi->createRequest(ROUTE_ITEMS), jsonData);
+void ServerCommunicator::onGetReplySuccessful(const QString& path, const QJsonDocument doc) {
+  if (path == ROUTE_ITEMS) {
+    emit itemsFetched(doc.toJson());
+  } else {
+    qWarning() << "Can't match request path:" << path;
+  }
+}
 
-  QObject::connect(reply, &QNetworkReply::finished, [=]() {
-    if (reply->error() == QNetworkReply::NoError) {
-      QByteArray responseData = reply->readAll();
-      const QString message   = QString("POST successful! Response: %1").arg(responseData);
-      qInfo() << message;
-      emit postRequestSuccessful(responseData);
+void ServerCommunicator::onGetReplyFailure(const QString& path, const QString errorString) {
+  if (path == ROUTE_ITEMS) {
+    emit itemsFetchFailure(errorString);
+  } else {
+    qWarning() << "Can't match request path:" << path;
+  }
+}
+
+void ServerCommunicator::sendPostRequest(const QString& path, const QByteArray data) {
+  const QNetworkRequest request = m_serviceApi->createRequest(path);
+
+  m_restManager->post(request, data, this, [this, path](QRestReply& reply) {
+    if (reply.isSuccess()) {
+      int statusCode = reply.httpStatus();
+      qInfo() << "Request successful. Status code:" << statusCode;
+      const QJsonDocument doc = reply.readJson().value();
+      onPostReplySuccessful(path, doc);
     } else {
-      const QString message = QString("Error: %1").arg(reply->errorString());
-      qDebug() << message;
-      emit postRequestFailure(message);
+      if (reply.hasError()) {
+        const QString errorString = reply.errorString();
+        qWarning() << "Network error:" << errorString;
+        onPostReplyFailure(path, errorString);
+      } else {
+        int statusCode = reply.httpStatus();
+        qWarning() << "Request not successful:" << statusCode;
+        qInfo() << "Content:" << reply.readJson();
+        if (statusCode == 401) {
+          notAuthorized(path);
+        } else {
+          onPostReplyFailure(path, QString("HTTP status code: %1").arg(statusCode));
+        }
+      }
     }
-    reply->deleteLater();
   });
 }
 
-void ServerCommunicator::deleteItem(const QString& id) {
-  const QString deleteRoute = QString("%1/%2").arg(ROUTE_ITEMS, id);
-  QNetworkReply* reply = m_restManager->deleteResource(m_serviceApi->createRequest(deleteRoute));
+void ServerCommunicator::onPostReplySuccessful(const QString& path, const QJsonDocument doc) {
+  if (path == ROUTE_ITEMS) {
+    emit sendItemSuccessful(doc.toJson());
+  } else if (path == ROUTE_LOG_IN) {
+    qCritical() << "Login success:" << doc.toJson(QJsonDocument::Compact);
+    emit loginSuccessful(doc.toJson(QJsonDocument::Compact));
+  } else {
+    qWarning() << "Can't match request path:" << path;
+  }
+}
 
-  QObject::connect(reply, &QNetworkReply::finished, [=]() {
-    if (reply->error() == QNetworkReply::NoError) {
-      QByteArray responseData = reply->readAll();
-      const QString message   = QString("DELETE successful! Response: %1").arg(responseData);
-      qInfo() << message;
-      emit deleteRequestSuccessful(responseData);
+void ServerCommunicator::onPostReplyFailure(const QString& path, const QString errorString) {
+  if (path == ROUTE_ITEMS) {
+    emit sendItemFailure(errorString);
+  } else if (path == ROUTE_LOG_IN) {
+    qCritical() << "Login failure:" << errorString;
+    emit loginFailure(errorString);
+  } else {
+    qWarning() << "Can't match request path:" << path;
+  }
+}
+
+void ServerCommunicator::sendDeleteRequest(const QString& path) {
+  const QNetworkRequest request = m_serviceApi->createRequest(path);
+  m_restManager->deleteResource(request, this, [this, path](QRestReply& reply) {
+    if (reply.isSuccess()) {
+      qInfo() << "Request successful.";
+      const QJsonDocument doc = reply.readJson().value();
+      onDeleteReplySuccessful(path, doc);
     } else {
-      const QString message = QString("Error: %1").arg(reply->errorString());
-      qDebug() << message;
-      emit deleteRequestFailure(message);
+      if (reply.hasError()) {
+        const QString errorString = reply.errorString();
+        qWarning() << "Network error:" << errorString;
+        onDeleteReplyFailure(path, errorString);
+      } else {
+        int statusCode = reply.httpStatus();
+        qWarning() << "Request not successful:" << statusCode;
+        if (statusCode == 401) {
+          notAuthorized(path);
+        } else {
+          onDeleteReplyFailure(path, QString("HTTP status code: %1").arg(statusCode));
+        }
+      }
     }
-    reply->deleteLater();
   });
-}
\ No newline at end of file
+}
+
+void ServerCommunicator::onDeleteReplySuccessful(const QString& path, const QJsonDocument doc) {
+  if (path.startsWith(ROUTE_ITEMS)) {
+    emit deleteItemSuccessful(doc.toJson());
+  } else {
+    qWarning() << "Can't match request path:" << path;
+  }
+}
+
+void ServerCommunicator::onDeleteReplyFailure(const QString& path, const QString errorString) {
+  if (path.startsWith(ROUTE_ITEMS)) {
+    emit deleteItemFailure(errorString);
+  } else {
+    qWarning() << "Can't match request path:" << path;
+  }
+}
diff --git a/network/servercommunicator.h b/network/servercommunicator.h
index 83f8be7..77b4d00 100644
--- a/network/servercommunicator.h
+++ b/network/servercommunicator.h
@@ -23,18 +23,26 @@ class ServerCommunicator : public QObject {
 
  public slots:
   void fetchItems();
-  void postItems(const QByteArray& jsonData);
+  void sendItem(const QByteArray& jsonData);
   void deleteItem(const QString& id);
+  // NEXT editItem(const QByteArray& jsonData)
 
  signals:
   void urlChanged();
 
+  void loginSuccessful(const QByteArray responseData);
+  void loginFailure(const QString errorString);
+
+  void notAuthorized(const QString path);
+
   void itemsFetched(const QByteArray jsonDoc);
   void itemsFetchFailure(const QString errorString);
-  void postRequestSuccessful(const QByteArray responseData);
-  void postRequestFailure(const QString errorString);
-  void deleteRequestSuccessful(const QByteArray responseData);
-  void deleteRequestFailure(const QString errorString);
+
+  void sendItemSuccessful(const QByteArray responseData);
+  void sendItemFailure(const QString errorString);
+
+  void deleteItemSuccessful(const QByteArray responseData);
+  void deleteItemFailure(const QString errorString);
 
  private:
   QNetworkAccessManager m_netManager;
@@ -44,6 +52,20 @@ class ServerCommunicator : public QObject {
   QString m_email;
   QString m_password;
   QString m_authToken;
+
+  bool validLoginCredentials();
+
+  void sendGetRequest(const QString& path);
+  void onGetReplySuccessful(const QString& path, const QJsonDocument doc);
+  void onGetReplyFailure(const QString& path, const QString errorString);
+
+  void sendPostRequest(const QString& path, const QByteArray data);
+  void onPostReplySuccessful(const QString& path, const QJsonDocument doc);
+  void onPostReplyFailure(const QString& path, const QString errorString);
+
+  void sendDeleteRequest(const QString& path);
+  void onDeleteReplySuccessful(const QString& path, const QJsonDocument doc);
+  void onDeleteReplyFailure(const QString& path, const QString errorString);
 };
 
 #endif  // SERVERCOMMUNICATOR_H