douwen2158 2018-07-24 19:08
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在程序MQTT期间更改订阅主题

I have a MQTT Go program that is subscribed to the topic "info", in which I receive a JSON message. I validate that JSON message, and if the validation is successful, I want to start subscribing to a new topic "info_updates". Here is my subscribing code:

func Info(){
    c := make(chan os.Signal, 1)
    signal.Notify(c, os.Interrupt, syscall.SIGTERM)

    opts := MQTT.NewClientOptions().AddBroker("tcp://test.mosquitto.org:1883")

    opts.SetDefaultPublishHandler(f)
    topic := "info" //I want to be able to change this later to "info_updates"

    opts.OnConnect = func(c MQTT.Client) {
        if token := c.Subscribe(topic, 0, f); token.Wait() && token.Error() != nil {
            panic(token.Error())
        }
    }
    // Creating new client
    client := MQTT.NewClient(opts)
    if token := client.Connect(); token.Wait() && token.Error() != nil {
        panic(token.Error())
    } else {
        fmt.Printf("Connected to server
")
    }
    <-c

}

Here is the code where I validate the JSON (parts of it):

var f MQTT.MessageHandler = func(client MQTT.Client, msg MQTT.Message) {
var integrationResult string

        if JSONValidate(msg.Payload())[0] == ""{ //sanity check = successful
         integrationResult = "successful"
        }else{ //sanity check = unsuccessful
        integrationResult = "unsuccessful"
        }

//do something here to tell the first function to change subscribing topic if integrationResult = "successful"

}

Note: func Info() and MQTT.MessageHandler are in two seperate files. I am stumped on how I can communicate with func Info() to change the topic subscription. Thank you.

  • 写回答

1条回答 默认 最新

  • du8589840 2018-07-25 17:22
    关注

    In my message.Handler, I do:

    if integrationResult == "unsuccessful"{
            client.Subscribe("data_update/" + deviceID, 0, g)
        }
    

    Where g is a new message.Handler. With this method, I not sure whether the first connection (subscription to info) is disconnected, or whether both connections are open. However, if you are just looking to get messages from a new topic, this a fine way.

    评论

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