MQTT is an excellent solution for connection of multiple devices.
Tutorial about MQTT: [IoT] MQTT Protocol
The rMQTT library, which is based on PubSubClient open source project, makes it simple to connect to a MQTT broker.
The first step is to connect to the network (not server) as described in this tutorial: https://www.b4x.com/android/forum/threads/ethernet-network-tutorial.65664/
The next step is to initialize MqttClient and call Connect:
The above code will reconnect automatically if the connection has broken.
The B4J code with the broker:
Tutorial about MQTT: [IoT] MQTT Protocol
The rMQTT library, which is based on PubSubClient open source project, makes it simple to connect to a MQTT broker.
The first step is to connect to the network (not server) as described in this tutorial: https://www.b4x.com/android/forum/threads/ethernet-network-tutorial.65664/
The next step is to initialize MqttClient and call Connect:
B4X:
'ethClient is an unconnected EthernetSocket object.
mqtt.Initialize(ethClient.Stream, serverIp, serverPort, "arduino", "Mqtt_MessageArrived", "Mqtt_Disconnected")
Sub Connect(unused As Byte)
If mqtt.Connect = False Then
Log("trying to connect again")
CallSubPlus("Connect", 1000, 0)
Return
End If
Log("Connected to broker")
mqtt.Subscribe("arduino", 0)
End Sub
Sub Mqtt_MessageArrived (Topic As String, Payload() As Byte)
Log("Message arrived. Topic=", Topic, " payload: ", Payload)
End Sub
Sub Mqtt_Disconnected
Log("Disconnected")
mqtt.Close
Connect(0)
End SubThe above code will reconnect automatically if the connection has broken.
The B4J code with the broker:
B4X:
Sub Process_Globals
Private broker As MqttBroker
Private client As MqttClient
End Sub
Sub AppStart (Args() As String)
broker.Initialize("", 51042)
broker.DebugLog = False
broker.Start
client.Initialize("client", "tcp://127.0.0.1:51042", "pc")
client.Connect
StartMessageLoop
End Sub
Sub Client_Connected (Success As Boolean)
If Success Then
client.Subscribe("pc", 0)
End If
End Sub
Sub Client_MessageArrived (Topic As String, Payload() As Byte)
If Topic = "pc" Then
If Payload(0) = 0 Then
Log("Button is down")
Else
Log("Button is up")
End If
client.Publish("arduino", "thank you for your message".GetBytes("utf8"))
End If
End Sub