如何使用 MQTT 发送唯一消息？

Question

i need your help. I am creating a program with MQTT, it must execute commands written on a file and send the result to a topic. I have already managed to execute the command and print the result on the terminal, but when I have to send it via MQTT it creates two messages, is it possible to send a message only with the result? how can I do? thanks I'll put the code for reading the result of the command executed and the two messages it sends me.

String result;
while ((result=reader.readLine()) != null) {
  System.out.println(result);
  final  MqttTopic timeTopic = client.getTopic(TOPIC);
  timeTopic.publish(new MqttMessage(result.getBytes()));
  System.out.println(" - Published data. Topic: " + timeTopic.getName() + "  Message: " + result);
}

Answer 1

The code you have is a line at a time, if the command outputs multiple lines then you are going to send multiple messages.

You need to loop over the output from reader.readLine() store all the results and then publish the message.

String line;
String output = "";
while ((line=reader.readLine()) != null) {
  System.out.println(line);
  output += line + "\n";
}
final MqttTopic timeTopic = client.getTopic(TOPIC);
timeTopic.publish(new MqttMessage(line.getBytes()));
System.out.println(" - Published data. Topic: " + timeTopic.getName() + "  Message: " + result);