I am developing a packaged app for chromebook. I am using BLE APIs to communicate with BLE devices. One of the modes of communication is request-response. Request is sent on a write characteristic and its response is received on another read characteristic. If multiple consecutive requests elicit same response then the notification is received only once.
For example consider request data bytes are [2, 5, 0] and its response is [3, 5, 0]. If I send [2,5,0] multiple times to the BLE device, and the device sends its response same number of times, in the chromebook app I see the characteristic notification only once.
Notification listener function:
chrome.bluetoothLowEnergy.onCharacteristicValueChanged.addListener(function (chrc) {
logger.info("char value changed " + chrc.uuid + " value " + chrc.value.byteLength + " address " + chrc.service.deviceAddress);
var data = new Uint8Array(chrc.value);
logger.info("Got char data " + data);
});
Char write function:
var myBytes = new Uint8Array([50, 20, 1]);
chrome.bluetoothLowEnergy.writeCharacteristicValue(charToWrite.instanceId, myBytes.buffer, function () {
if (chrome.runtime.lastError) {
logger.error("Failed to write value: " + chrome.runtime.lastError.message);
return;
}
logger.info("First char write done");
chrome.bluetoothLowEnergy.writeCharacteristicValue( charToWrite.instanceId, myBytes.buffer, function () {
if (chrome.runtime.lastError) {
logger.error("Failed to write value: " + chrome.runtime.lastError.message);
return;
}
logger.info("Second char write done");
});
});
In above example, the notification response for second char write is never received (since the command is the same, the response is also the same).
If I send another command which elicits different response, then notification is received correctly.
Same BLE communication works fine on other platforms like Windows, MacOS. Thus we know that there is no device side issue. Chromebook seems to suppress notifications if same data is received on characteristic again and again.
I could not find a way in chromebook BLE API to change this behavior.
Has anybody else also seen this issue?
Related
So I am using the Arduino Uno and the ESP8266 module. I am trying to get the module to send an HTTP get request using the AT serial firmware however I am not quite able to do so. The project gets data from a sensor and sends it in real time using the Pubnub Service by posting the data to the pubnub rest API.
I have the function:
void sendSerialCommand(String cmd, int t) {
int i=0;
while(1) {
Serial.println(cmd);
client.println(cmd);
while(client.available()) {
if(client.find("OK"))
i=8;
}
delay(t);
if(i>5)
break;
i++;
}
if(i==8)
Serial.println("OK");
else
Serial.println("Error");
}
Using this function, I set up a connection with the server as :
sendSerialCommand("AT+CIPMUX=1",100);
sendSerialCommand("AT+CIPSTART=0,\"TCP\",\"" + pubnubIP + "\",80",1000);
Serial.println("Established connection with DashBoard Servers.....");
Then I try:
sendSerialCommand("AT+CIPSEND=0," + String(getRequestLength) + "," + "http://" + pubnubIP + "/publish/<publish-key>/<sub-key>/0/water/0/<data>", 1000);
(I have put in the values for the publish and sub key in the actual code.)
The getRequestLength is the length of the data to be sent.
When I run the code, the output says wait..... and the the connection just closes. Could anyone please tell me the correct Syntax or method of sending the data?
How one forces Windows to disconnect from BLE device being used in UWP app? I receive notifications from some characteristics but at some point I want to stop receiving them and make sure I disconnect from the BLE device to save BLE device's battery?
Assuming your application is running as a gatt client and you have the following instances your are working with in your code:
GattCharacteristic myGattchar; // The gatt characteristic you are reading or writing on your BLE peripheral
GattDeviceService myGattServ; // The BLE peripheral' gatt service on which you are connecting from your application
BluetoothLEDevice myBleDev; // The BLE peripheral device your are connecting to from your application
When you are already connected to your BLE peripheral, if you call the Dispose() methods like this :
myBleDev.Dispose(); and/or myGattServ.Dispose(); and/or myGattchar.Service.Dispose()
you surely will free resources in your app but will not cleanly close the BLE connection: The application looses access to control resources for the connection. Nevertheless, connection remains established on the lower levels of the stack (On my peripheral device the Bluetooth connection active LED remains ON after calling any of Dispose() methods).
Forcing disconnection is done by first disabling notifications and indications on the concerned characteristic (i.e. myGattchar in my example above) by writing a 0 (zero) to the Client Characteristic Configuration descriptor for that characteristic through call to method WriteClientCharacteristicConfigurationDescriptorAsync with parameter GattClientCharacteristicConfigurationDescriptorValue.None :
GattCommunicationStatus status =
await myGattchar.WriteClientCharacteristicConfigurationDescriptorAsync(
GattClientCharacteristicConfigurationDescriptorValue.None);
Just dispose all objects related to the device. That will disconnect the device, unless there are other apps connected to it.
For my UWP app, even though I've used Dispose() methods, I still received notifications. What helped me was setting my device and characteristics to null. Example:
device.Dispose();
device = null;
Not all to certain of how "correct" this programming is, but it's been working fine for me so far.
The UWP Bluetooth BLE sample code from Microsoft (dispose the BLE device) didn't work for me. I had to add code (dispose the service) to disconnect the device.
private async Task<bool> ClearBluetoothLEDeviceAsync()
{
if (subscribedForNotifications)
{
// Need to clear the CCCD from the remote device so we stop receiving notifications
var result = await registeredCharacteristic.WriteClientCharacteristicConfigurationDescriptorAsync(GattClientCharacteristicConfigurationDescriptorValue.None);
if (result != GattCommunicationStatus.Success)
{
return false;
}
else
{
selectedCharacteristic.ValueChanged -= Characteristic_ValueChanged;
subscribedForNotifications = false;
}
}
selectedService?.Dispose(); //added code
selectedService = null; //added code
bluetoothLeDevice?.Dispose();
bluetoothLeDevice = null;
return true;
}
Remember you must call -= for events you have called += or Dispose() will never really garbage collect correctly. It's a little more code, I know. But it's the way it is.
Not just with bluetooth stuff, I will remind you - with everything. You can't have hard referenced event handlers and get garbage collection to work as expected.
Doing all the disposing and null references suggested didn't achieve the Windows (Windows Settings) disconnection I was looking for.
But dealing with IOCTL through DeviceIoControl did the job.
I found that after calling GattDeviceService.GetCharacteristicsAsync(), BluetoothLeDevice.Dispose() does not work. So I dispose the Service I don't need.
GattCharacteristicsResult characteristicsResult = await service.GetCharacteristicsAsync();
if (characteristicsResult.Status == GattCommunicationStatus.Success)
{
foreach (GattCharacteristic characteristic in characteristicsResult.Characteristics)
{
if (characteristic.Uuid.Equals(writeGuid))
{
write = characteristic;
}
if (characteristic.Uuid.Equals(notifyGuid))
{
notify = characteristic;
}
}
if (write == null && notify == null)
{
service.Dispose();
Log($"Dispose service: {service.Uuid}");
}
else
{
break;
}
}
Finally, when I want to disconnect the Bluetooth connection
write.Service.Dispose();
device.Dispose();
device = null;
I have a setup which uses the ESP8266 12E and it opens a web server at a specific port 200. I have used the port forwarding to route the incoming data to this server .And I have used the duckdns to register the IP and call the duckdns domain to trigger the ESP.
This works fine and I am able to trigger using the following
http://mydomain.duckdns.org:200/parseIFTTT
Using the postman tool, with the contentType as plain/text and the method as POST what ever contents I pass are getting parsed by parseIFTTT method in the ESP
void parseIFTTT() {
String message;
message += server.args();
message += "\n";
for (uint8_t i = 0; i < server.args(); i++) {
message += " " + server.argName(i) + ": " + server.arg(i) + "\n";
}
Serial.println(message);
server.send(200, "text/plain", "Success");
}
But when tried to integrate with IFTTT for any Facebook or gmail events, I am not able to parse the data from IFTTT.
The request goes to ESP8266 but the request data I am not able to parse.
The following is the request :
URL : http://mydomain.duckdns.org:200/parseIFTTT
Method : POST
Content Type: text/plain
Body : {{Message}}
In the body I have just added the {{Message}} only. In the serial monitor I get the op as blank
1
plain:
I found the issue after a lot of debugging.
The esp8266\hardware\esp8266\2.2.0\libraries\ESP8266WebServer\src\Parsing.cpp
in the core library for the Http server was using the 'Content-Length' and IFTTT was sending the request header with name as "content-length' and hence the content length was not retrieved and the parsed data was not retrieved.
Not sure whether its an issue with the IFTTT where they send this as a lower cased value.
We are trying to run the sample app for push notifications with some modification to get it to send out a broadcast notification, but it is not getting sent.
We have modified the PushBackendEmulator code as well. The emulator invokes the submitBroadCastNotification procedure successfully and the following result is returned:
Server response :: /-secure-{"result":"Notification sent to all
users","isSuccessful":true}/
However, it appears the WL.Server.sendMessage method is not sending the message and returns. I am not able to see the server side logs either after a thorough search on the liberty server except for the messages.log on the liberty server which shows the following when WL.Server.sendMessage is called.
ht.integration.js.JavaScriptIntegrationLibraryImplementation E
FWLSE0227E: Failed to send notification. Reason: FPWSE0009E: Internal
server error. No devices found [project worklight]
Here is the adapter code:
function submitBroadcastNotification( notificationText) {
var notification = {};
notification.message = {};
notification.message.alert = notificationText;
//notification.target = {};
//notification.target.tagNames = ['test'];
WL.Logger.debug("broadcast: " + notification.message.alert );
var delayTimeOut = **WL.Server.sendMessage**("PushNotificationsApp", notification);
WL.Logger.debug("Return value from WL.Server.sendMessage :"+ delayTimeOut);
return {
result : "Notification sent to all users"
};
}
Here is the PushBackendEmulator code:
public static void main(String [] args){
String serverUrl =
"http://208.124.245.78:9080/worklight";
String notificationText = "Hellofrombroadcastingnotifications";
String userId = "admin";
notificationText = notificationText.replace(" ", "%20");
Logger.debug("sending broadcast notification: " + notificationText);
URL url = new URL(serverUrl
+ "/invoke?
adapter=PushAdapter&procedure=submitBroadcastNotification¶meters=['" + userId + "','" + notificationText + "']");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setReadTimeout(10000);
connection.setDoOutput(true);
Logger.debug("Connected to server");
BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String response = "";
String inputLine;
while ((inputLine = in.readLine()) != null)
response+= inputLine;
Logger.debug("response is:"+ response);
in.close();
Logger.debug("Server response :: " + response);
connection.disconnect();
Looking at your application from the PMR, it seems to me like you have mixed both event source-based notifications and broadcast notifications.
If you want to use Broadcast notifications, this means you cannot try imposing sending the notification to any specific userId, etc as it is not needed nor based on userIds.
By default, all devices are auto-subscribed to a tag called "push.ALL".
You can read more about broadcast notifications API methods in the IBM Worklight Knowledge Center.
This is a modified version of your application, tested in iOS and Android: https://www.dropbox.com/s/l2yk2pbvykrzfoh/broadcastNotificationsTest.zip?dl=0
Basically, I stripped away from it anything not related to broadcast notifications:
I removed the push securitytest from application-descriptor.xml
I removed any function from the adapter XML and JS files and main.js file that is related to event source-based notifications.
The end result is that after the app is loaded, you are right inside the application (no login).
I then right-clicked the adapter folder in Studio > invoke procedure, and selected the submitBroadcastNotification option to send the notification ("aaa").
In the device, a notification was received. Tapping it (if the app is closed) launches the application, which then triggers the WL.Client.Push.onMessage API in common\js\main.js to display alerts containing the payload and props of the received notification.
This was tested in both iOS and Android.
As the application was loading, I could see in LogCat and Xcode console the token registration.
To test this in iOS, you will need to update application-descriptor.xml with your own pushSender password and add your own apns-certificatae-sandbox.p12 file.
To test in Android, make sure you are have generated a browser key in the GCM console and are using it in application-descriptor.xml
For both, make sure that all requires ports and addresses and accessible in your network
I am developing a vehicle tracking system which uses GPS/GPRS/GSM. The tracking device I am currently using is GV100, a GPS/GPRS/GSM tracker from Quectel ([www.quectel.com][1].)
I am not able to establish connection between the device and the backend server. My question particularly is:
How do I send commands (AT Commands) to the device from the server?
How do I accept the response (reports and acknowledgement messages) from the device to save it in the database?
I sent command to the device with the MGV100 Manage Tool (Software provided by Quectel) via serial port. And I got acknowledgement SMS message on GSM enabled mobile telephone. Now, I want to send message from the server and accept reply on the server (not by SMS). I don’t know how to send command and receive the reply. I have no previous experience in developing such systems.
It would be great if I can get a sample code and setup procedures if it requires.
Where can I get a relevant tutorial for the case I mentioned?
Thanks jhonkola
To understand how server receives and send data to the device, I decided to first implement the communication between the client (currently my PC) and server. Though my ultimate goal is communicating with the device, currently I am trying to establish connection from my PC to the server. If I succeed in this, I will strive to communicate to server from the device which needs IP address and port number of server to send and receive data.
This is my assumption how to do it:
I can open a port on the server from .cs code so as to communicate
using TCP/UDP.
Client then can send and receive data via this
port.
I can save the data sent from the client on server's file
system and review it any time. (Am not storing the data in relational database because I don't want to bother about database issues now.)
This is how I tried to implement:
Server a C# Web Application:
When a button is clicked it opens a port and listens to client
protected void btnConnect_Click(object sender, EventArgs e)
{
try
{
continueListening = true;
while (continueListening)
{
int port=Int32.Parse(txtPort.Text);
lblOutput.Text = "Port is now " + port +". Waiting for connection";
TcpListener myList = new TcpListener(IPAddress.Parse(txtIpAddress.Text), port);
myList.Start();
Socket s = myList.AcceptSocket();
lblOutput.Text="Connection accepted from " + s.RemoteEndPoint;
byte[] b = new byte[100];
int k = s.Receive(b);
lblOutput.Text = ("Recieved...");
String obtainedText = "";
for (int i = 0; i < k; i++)
{
obtainedText = obtainedText + " " + (Convert.ToChar(b[i]));
}
writeToTextFile("C:/Users/MekAtIbex/Desktop/TESTED/RECIEVED.txt", obtainedText);
lblOutput.Text = obtainedText;
ASCIIEncoding asen = new ASCIIEncoding();
lblOutput.Text = lblOutput.Text +" "+ ("The string was recieved by the server.");
lblOutput.Text = lblOutput.Text +" "+ ("\r\nSent Acknowledgement");
}
Client: C# Windows application
private void btnSend_Click(object sender, EventArgs e)
{
try
{
TcpClient tcpClient = new TcpClient();
int port=Int32.Parse(txtPort.Text.Trim());
tcpClient.Connect(txtIpAddress.Text, port);
lblStatus.Text = ("Connected");
Stream stm = tcpClient.GetStream();
ASCIIEncoding asen = new ASCIIEncoding();
byte[] bytesToSend = asen.GetBytes(txtData.Text);
lblStatus.Text = ("Transmitting.....");
stm.Write(bytesToSend, 0, bytesToSend.Length);
byte[] bb = new byte[100];
int k = stm.Read(bb, 0, 100);
for (int i = 0; i < k; i++)
{
txtaResponse.Text = txtaResponse.Text + "\n" + "Res... " + new DateTime() + " " + Convert.ToChar(bb[i]);
Console.Write(Convert.ToChar(bb[i]));
}
tcpClient.Close();
}
catch (Exception ex)
{
lblStatus.Text = ("Connected");
txtaRequest.Text = txtaRequest.Text + "\n" + "Err... " + new DateTime() + " " + ex.StackTrace;
}
}
My current questions are:
Is my assumption correct? If not how should I do it?
I have tried to save it using the above code but I didn't got the file.
What is the advantage and disadvantage of using UDP in comparison TCP for tracking applications?
I have browsed well, but I couldn't find a place for a good start. And, as I have no experience in such applications, I couldn't debug my application.
My current questions are:
Is my assumption correct? If not how should I do it?
Yes, your basic assumptions are correct. The server would open a listening port and then the client could connect to this port and drop off data as needed. You can have the server log this to a file for later review too.
I have tried to save it using the above code but I didn't got the
file.
Is the file already created? The method you have will fail if the file is not existent on the system.
What is the advantage and disadvantage of using UDP in comparison TCP
for tracking applications?
UPD is less expensive in terms of network setup. It is the "fast and dirty" method of communication. The downside is that you may not get every message properly delivered. In some applications, this just doesn't matter and the benefits are worth this cost.
Now a few things I'd change:
Change IPAddress.Parse(txtIpAddress.Text) to IPAddress.Any
This will allow your listener the broadest ability to catch incoming messages and will most likely not effect other systems (since this is essentially your first networking program).
You'll also want to make your listener spawn a thread to handle the file writing and then go back to listening. This is a very standard practice and allows for servers to handle multiple connections.
It is difficult to comprehensively answer this, as a good answer would require detailed knowledge about the product. I suggest that you contact the manufacturer / reseller for support.
A few general points:
Sending commands over network to the device requires that you are able to connect to the device from internet. This is not always easy over GSM network, as the operators may block all incoming traffic. The manufacturer may have provided solutions for this.
If you can connect to the device, the protocol that is used to give commands (assuming that such protocol is built-in) will also contain a mechanism to receive any responses.