CALL an ASHX Handler

Sub PostString(JobName As String, URL As String, Text As String, ContentType As String)
    PostBytes(JobName, URL, Text.GetBytes("UTF8"), ContentType)
End Sub

Sub PostBytes(JobName As String, URL As String, Data() As Byte, ContentType As String)
    If internalCheckIfCanStart(JobName) = False Then Return
    HttpUtilsService.PostInputStream = Null
    HttpUtilsService.PostBytes = Data
    HttpUtilsService.ContentType = ContentType
    Tasks = Array As String(URL)
    HttpUtilsService.Post = True
    StartService(HttpUtilsService)
End Sub

Sub Process_Globals
    '--- Under the existing lines you will find here..
    Dim ContentType As String '--- Add this line
End Sub

Sub ProcessNextTask
    If finishTasks >= HttpUtils.Tasks.Size Then
        HttpUtils.Working = False
        HttpUtils.Complete = True
        'Raise job done event
        If HttpUtils.CallbackJobDoneSub <> "" Then
            CallSub2(HttpUtils.CallbackActivity, HttpUtils.CallbackJobDoneSub, HttpUtils.Job)
        End If
        'If no new job was started then we kill this service.
        If HttpUtils.Working = False Then
            StopService("")
        End If
        Return
    End If
    If task >= HttpUtils.Tasks.Size Then Return
    Dim link As String
    link = HttpUtils.Tasks.Get(task)
    Dim req As HttpRequest
    If Post Then
        If PostInputStream.IsInitialized Then
            req.InitializePost(link, PostInputStream, PostLength)
        Else
            req.InitializePost2(link, PostBytes)
            req.SetContentType(ContentType) '--- Add this line
        End If
    Else
        req.InitializeGet(link)
    End If
    'Here you can modify the request object if needed
    countWorking = countWorking + 1
    taskToRequest.Put(task, link)
    hc.Execute(req, task)
    task = task + 1
End Sub

    Dim ContentType As String: ContentType = "application/json"

    Dim objMap As Map: objMap.Initialize
    objMap.Put("DEVICENAME", SomeDeviceName)
    Dim objJSon As JSONGenerator: objJSon.Initialize(objMap)
    HttpUtils.PostString("SomeString", "YourASHXURL", objJSon.ToString, ContentType)