Android Question Send firebase notification to a specific client.

Public Sub SubscribeToTopics
    topic = Starter.DeviceID
    Sleep(0)
    Do While fm.Token = Null
        Sleep(500)
    Loop
    Dim token As String = fm.Token
    Log("SubscribeToTopics fm-token = "&token)
    

    If token <> "" Then
        Log("Register Device with Token: "&token)
        Dim j As HttpJob
        j.Initialize("",Me)
        j.Download2(Starter.BridgeURL,Array As String("action","register","token",fm.Token,"deviceID",Starter.DeviceID))
        wait for (j) JobDone(job As HttpJob)
        If job.Success Then
            Dim res As String = job.GetString
            Log("Register Successfully")
            Log(job.GetString)

            job.Release
        Else
            LogColor("Error: "&job.ErrorMessage, Colors.Red)
            job.Release
        End If
    End If
    fm.SubscribeToTopic(token) 'you can subscribe to more topics
    fm.SubscribeToTopic(topic) 'you can subscribe to more topics
End Sub

Private Sub SendMessage(id As String, Title As String, Body As String)
    Dim API_KEY As String="Your Key"   
    Dim Job As HttpJob
    Job.Initialize("fcm", Me)
    Dim m As Map = CreateMap("to": $"${id}"$)
    Dim data As Map = CreateMap("title": Title, "body": Body)
    m.Put("data", data)
    Dim jg As JSONGenerator
    jg.Initialize(m)
    Job.PostString("https://fcm.googleapis.com/fcm/send", jg.ToString)
    Job.GetRequest.SetContentType("application/json;charset=UTF-8")
    Job.GetRequest.SetHeader("Authorization", "key=" & API_KEY)
End Sub