Improve naming on ping command

With the addition of the `device` command it could be confusing what
`username` and `password` refer to (are they a virtual device's ID and
secret or are they an IoT API client ID and secret?).

Author: Giuseppe Lumia

README.md

@@ -36,7 +36,7 @@ Use this command to provision a device:
 The iot-cloud-cli can be used as a virtual device for Arduino IoT Cloud for testing.
 
 ```
-$ iot-cloud-cli ping -u "<deviceId>" -p "<secret>" -t <thing ID>>
+$ iot-cloud-cli ping -d "<deviceId>" -s "<secret>" -t <thing ID>>
   Connected to Arduino IoT Cloud
   Subscribed true
   Property value sent successfully 81
@@ -71,7 +71,7 @@ You should connect the new device to the new thing.
 ##### Connect to the PROD environment
 
 ```shell
-$ iot-cloud-cli ping -u "<Device ID>" -p "<Secret Key>" -t <Thing ID>>
+$ iot-cloud-cli ping -d "<Device ID>" -s "<Secret Key>" -t <Thing ID>>
 ```
 
 If every works as expected you should see something similar to this output:
@@ -89,5 +89,5 @@ If you visit https://create.arduino.cc/iot/devices the "Generic ESP8266 Module"
 The DEV environment is using a different broker, so you need to add the option `--host`:
 
 ```shell
-$ iot-cloud-cli ping --host tcps://mqtts-sa.iot.oniudra.cc:8884 -u "<Device ID>" -p "<Secret Key>" -t "<thing-id>"
+$ iot-cloud-cli ping --host tcps://mqtts-sa.iot.oniudra.cc:8884 -d "<Device ID>" -s "<Secret Key>" -t "<thing-id>"
 ```

cli/ping/ping.go

@@ -7,9 +7,9 @@ import (
 
 var (
 	host            string
-	username        string
-	password        string
-	thingID         string
+	device          string
+	secret          string
+	thing           string
 	troubleshooting bool
 )
 
@@ -21,26 +21,26 @@ func NewCommand() *cobra.Command {
 		RunE:  runPingCommand,
 	}
 
-	pingCommand.Flags().StringVarP(&host, "host", "b", "tcps://mqtts-up.iot.arduino.cc:8884", "Broker endpoint")
-	pingCommand.Flags().StringVarP(&username, "username", "u", "", "Username (required)")
-	pingCommand.Flags().StringVarP(&password, "password", "p", "", "Password (required)")
-	pingCommand.Flags().StringVarP(&thingID, "thing_id", "t", "", "Thing ID (required)")
+	pingCommand.Flags().StringVarP(&host, "host", "b", "tcps://mqtts-up.iot.arduino.cc:8884", "MQTT Broker URL")
+	pingCommand.Flags().StringVarP(&device, "device", "d", "", "Device ID")
+	pingCommand.Flags().StringVarP(&secret, "secret", "s", "", "Device Secret")
+	pingCommand.Flags().StringVarP(&thing, "thing", "t", "", "Thing ID")
 
 	pingCommand.Flags().BoolVar(&troubleshooting, "troubleshooting", false, "Enable troubleshooting mode (full logs from the MQTT client)")
 
-	pingCommand.MarkFlagRequired("username")
-	pingCommand.MarkFlagRequired("password")
-	pingCommand.MarkFlagRequired("thing_id")
+	pingCommand.MarkFlagRequired("device")
+	pingCommand.MarkFlagRequired("secret")
+	pingCommand.MarkFlagRequired("thing")
 
 	return pingCommand
 }
 
 func runPingCommand(cmd *cobra.Command, args []string) error {
 	params := &ping.Params{
 		Host:            host,
-		Username:        username,
-		Password:        password,
-		ThingID:         thingID,
+		Username:        device,
+		Password:        secret,
+		ThingID:         thing,
 		Troubleshooting: troubleshooting,
 	}
 

command/ping/ping.go

@@ -15,11 +15,11 @@ import (
 )
 
 type Params struct {
-	Host            string
-	Username        string
-	Password        string
-	ThingID         string
-	Troubleshooting bool
+	Host            string // MQTT Broker URL
+	Username        string // Virtual device ID
+	Password        string // Virtual device secret
+	ThingID         string // ID of thing with `int` property named `counter` attached to the virtual device
+	Troubleshooting bool   // Enable/disable verbose logging of MQTT client
 }
 
 func Ping(params *Params) error {