How to invoke device method in ios using azure iot sdk - ios

Question

I am trying to call a method associated with the device using connection string.
I tried with the samples provided with other languages I am able to call the method in the device. eg: "setState" or "getState" of the lamp.
But I am not able to implement in iOS using swift.
I tried to match parameter parameter requirement by referring to the C sample. But I am getting
1. Func:sendHttpRequestDeviceMethod Line:337 Http Failure status code 400.
2. Func:IoTHubDeviceMethod_Invoke Line:492 Failure sending HTTP request for device method invoke
var status :Int32! = 0
var deviceId = "simulated_device_one";
var methodName = "GetState";
var uint8Pointer:UnsafeMutablePointer<UInt8>!
uint8Pointer = UnsafeMutablePointer<UInt8>.allocate(capacity:8)
var size = size_t(10000)
var bytes: [UInt8] = [39, 77, 111, 111, 102, 33, 39, 0]
uint8Pointer?.initialize(from: &bytes, count: 8)
var intValue : UnsafeMutablePointer<UInt8>?
intValue = UnsafeMutablePointer(uint8Pointer)
var char: UInt8 = UInt8(20)
var charPointer = UnsafeMutablePointer<UInt8>(&char)
var prediction = intValue
let serviceClientDeviceMethodHandle = IoTHubDeviceMethod_Create(service_client_handle)
let payLoad = "test"
var responsePayload = ""
let invoke = IoTHubDeviceMethod_Invoke(serviceClientDeviceMethodHandle, deviceId, methodName, payLoad , 100, &status, &prediction,&size )
I want to call a method in the device using IoTHubDeviceMethod_Invoke

Answer 1

You can download View controller file which I worked on from here
1.Create Connection in view did load
// declaring your connection string you can find it in azure iot dashboard
private let connectionString = "Enter your connection String";
// creating service handler
private var service_client_handle: IOTHUB_SERVICE_CLIENT_AUTH_HANDLE!;
// handler for the method invoke
private var iot_device_method_handle:IOTHUB_SERVICE_CLIENT_DEVICE_METHOD_HANDLE!;
// In view did load establish the connection
service_client_handle = IoTHubServiceClientAuth_CreateFromConnectionString(connectionString)
if (service_client_handle == nil) {
showError(message: "Failed to create IoT Service handle", sendState: false)
}
create method invoke function
I created it based on the demo provided for sending message
func openIothubMethodInvoke() -> Bool
{
print("In openIotHub method invoke")
let result: Bool;
iot_device_method_handle = IoTHubDeviceMethod_Create(service_client_handle);
let testValue : Any? = iot_device_method_handle;
if (testValue == nil) {
showError(message: "Failed to create IoT devicemethod", sendState: false);
result = false;
}
else
{
result = true;
}
return result;
}
call method invoke
** this is the main function for calling the method
func methodInvoke()
{
let testValue : Any? = iot_device_method_handle;
if (testValue == nil && !openIothubMethodInvoke() ) {
print("Failued to open IoThub messaging");
}
else {
let size = UnsafeMutablePointer<Int>.allocate(capacity: 1)
let responseStatus = UnsafeMutablePointer<Int32>.allocate(capacity: 1)
// Payload is the main change it is like specifying the format
var payload = UnsafeMutablePointer<UnsafeMutablePointer<UInt8>?>.allocate(capacity: 1)
// if payload is not expected please send empty json "{}"
let result = IoTHubDeviceMethod_Invoke(iot_device_method_handle, "nameOfTheDeviceYouWantToCallOn", "MethodName", "{payload you want to send}", 100, responseStatus, payload , size)
// extracting the data from response
let b = UnsafeMutableBufferPointer(start: payload.pointee, count: size.pointee)
let data = Data(buffer: b)
let str = String(bytes: data, encoding: .utf8)
print(str)
do{
let value = try JSONSerialization.jsonObject(with: data, options: .allowFragments)
print(value)
}catch{
print(error)
}
}
}

Answer 2

As discussed above: the payload needs to be valid JSON. Even an empty json will do such as {}