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我正在使用paho发送和接收mqtt消息.
到目前为止,发送消息没有问题,我通过使用mosquitto接收它们.
现在我想通过使用java客户端阅读消息,我注意到有关接收消息的文档较少.
我实现了MqttCallback接口,但我仍然无法弄清楚如何阅读我订阅的主题的消息.
这是我的源代码到目前为止,我可以使用mosquitto_sub读取消息.
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
public class PahoDemo implements MqttCallback {
MqttClient client;
MqttClient subClient;
public PahoDemo() {
}
public static void main(String[] args) {
new PahoDemo().doDemo();
}
public void doDemo() {
try {
client = new MqttClient("tcp://192.168.118.11:1883", "Sending");
subClient = new MqttClient("tcp://192.168.118.11:1883",
"Subscribing");
client.connect();
subClient.connect();
subClient.subscribe("foo");
MqttMessage message = new MqttMessage();
message.setPayload("A single message from my computer fff"
.getBytes());
client.publish("foo", message);
client.disconnect();
client.close();
subClient.disconnect();
subClient.close();
} catch (MqttException e) {
e.printStackTrace();
}
}
@Override
public void connectionLost(Throwable cause) {
// TODO Auto-generated method stub
}
@Override
public void messageArrived(String topic, MqttMessage message)
throws Exception {
System.out.println(message);
}
@Override
public void deliveryComplete(IMqttDeliveryToken token) {
// TODO Auto-generated method stub
}
}
解决方法:
在经纪人有时间发回消息之前,您正在关闭客户端.
此外,您不需要2个客户端实例,只需一个即可发送和接收.
我已经编辑了一点代码,它现在将继续运行并接收消息,直到你杀了它.
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
public class PahoDemo implements MqttCallback {
MqttClient client;
public PahoDemo() {
}
public static void main(String[] args) {
new PahoDemo().doDemo();
}
public void doDemo() {
try {
client = new MqttClient("tcp://192.168.118.11:1883", "Sending");
client.connect();
client.setCallback(this);
client.subscribe("foo");
MqttMessage message = new MqttMessage();
message.setPayload("A single message from my computer fff"
.getBytes());
client.publish("foo", message);
} catch (MqttException e) {
e.printStackTrace();
}
}
@Override
public void connectionLost(Throwable cause) {
// TODO Auto-generated method stub
}
@Override
public void messageArrived(String topic, MqttMessage message)
throws Exception {
System.out.println(message);
}
@Override
public void deliveryComplete(IMqttDeliveryToken token) {
// TODO Auto-generated method stub
}
}
编辑：添加了缺少的client.setCallback(this)
标签：mqtt,java,eclipse
来源： https://codeday.me/bug/20190928/1826870.html