diff -r 000000000000 -r 7ef5ce9477c8 src/MQTTHandler.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/MQTTHandler.h	Fri May 06 21:54:32 2022 +0200
@@ -0,0 +1,88 @@
+/**
+ * Relational pipes
+ * Copyright © 2022 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+#include <memory>
+#include <string>
+#include <vector>
+#include <iostream>
+#include <sstream>
+#include <locale>
+#include <codecvt>
+
+#include <relpipe/common/type/typedefs.h>
+#include <relpipe/reader/TypeId.h>
+#include <relpipe/reader/handlers/RelationalReaderStringHandler.h>
+#include <relpipe/reader/handlers/AttributeMetadata.h>
+
+#include "MQTT.h"
+#include "Configuration.h"
+#include "Hex.h"
+
+namespace relpipe {
+namespace out {
+namespace mqtt {
+
+class MQTTHandler : public relpipe::reader::handlers::RelationalReaderStringHandler {
+private:
+	std::wstring_convert<codecvt_utf8<wchar_t>> convertor; // TODO: support also other encodings.
+	Configuration configuration;
+	shared_ptr<MQTT> mq;
+
+	struct CurrentRelation {
+		relpipe::common::type::StringX name;
+		std::vector<relpipe::reader::handlers::AttributeMetadata> attributes;
+		relpipe::common::type::Integer attributeIndex = 0;
+		std::string currentValue;
+	} currentRelation;
+
+public:
+
+	MQTTHandler(Configuration configuration) : configuration(configuration) {
+		// TODO: do not throw exception from the constructor: MQTT::open()
+		mq.reset(MQTT::open(convertor.to_bytes(configuration.queue), configuration.unlinkOnClose));
+	}
+
+	void startRelation(relpipe::common::type::StringX name, std::vector<relpipe::reader::handlers::AttributeMetadata> attributes) override {
+		currentRelation = CurrentRelation{name, attributes};
+	}
+
+	void attribute(const relpipe::common::type::StringX& value) override {
+
+		auto attributeName = currentRelation.attributes[currentRelation.attributeIndex].getAttributeName();
+		if (attributeName == L"text" && value.size()) currentRelation.currentValue = convertor.to_bytes(value);
+		else if (attributeName == L"data" && value.size()) currentRelation.currentValue = Hex::fromHex(value).str();
+		else if (attributeName == L"text"); // keep empty or value from 'data'
+		else if (attributeName == L"data"); // keep empty or value from 'text'
+
+		currentRelation.attributeIndex++;
+		if (currentRelation.attributeIndex == currentRelation.attributes.size()) {
+			currentRelation.attributeIndex = 0;
+			mq->send(currentRelation.currentValue);
+		}
+
+	}
+
+	void endOfPipe() {
+
+	}
+
+};
+
+}
+}
+}