从 MQTT 服务器接收消息时，Protobuf Java 方法 parseFrom() 挂起

Question

I'm currently trying to publish and receive Protobuf messages via a Mosquitto MQQT Server. I am succesfully publishing the proper to the Server. However, when a client receives it, the method parseFrom() hangs and never returns. This is a very similar issue to this one , occuring when a Protobuf message is sent via a Socket that's never closed.

Publisher :

MqttClient adapterClient = new MqttClient(broker, clientID);
SpecsMessage.Specs protoNotifyMessage = SpecsMessage.Specs.newBuilder()
                    .setNodeType("basic")
                    .setAddress(serverSocket.getInetAddress().getHostName())
                    .setPort(serverSocket.getLocalPort())
                    .build();
MqttMessage notifyMessage = new MqttMessage(protoNotifyMessage.toString().getBytes());
adapterClient.publish("availableNodes", notifyMessage);

Subscriber :

public class TestController implements MqttCallback {
  public void messageArrived(String topic, MqttMessage message){
                System.out.println("New node connected");     
                System.out.println("Payload: \n" + new String(message.getPayload()));                           
                SpecsMessage.Specs protoMessage = SpecsMessage.Specs.parseFrom(message.getPayload());
  }
}

I could not find a way to specify to the MQQT Server a correct way to send the message.

I also tried using the writeDelimitedFrom() method.

MqttClient adapterClient = new MqttClient(broker, clientID);
SpecsMessage.Specs protoNotifyMessage = SpecsMessage.Specs.newBuilder()
                    .setNodeType("basic")
                    .setAddress(serverSocket.getInetAddress().getHostName())
                    .setPort(serverSocket.getLocalPort())
                    .build();
ByteArrayOutputStream output = new ByteArrayOutputStream();
protoNotifyMessage.writeDelimitedTo(output);
MqttMessage notifyMessage = new MqttMessage(output.toByteArray());
adapterClient.publish("availableNodes", notifyMessage);

However, the message is not correctly converted in byte[], here's what it should look like :

nodeType: "basic"
address: "0.0.0.0"
port: 43101

And here's what I get :

basic0.0.0.0��

Is there a way to make this work, either by correcting the sending method or by solving the byte[] conversion problem?

Answer 1

You're trying to use parseFrom to parse the text-formatted proto. parseFrom is for parsing the wire format.

Send the proto in the wire format instead - message.toByteArray() .

(If you want to parse from the text format, use TextFormat ).