I'm developing a ble-based native local multiplayer plugin for Unity (for both Android and iOS). I use a single service, with a single characteristic with rw permissions. I've managed to make Android<->Android and iOS<->iOS work all right, but I'm having a rough time trying to make Android<->iOS work. Specifically, it's the 'iOS as Peripheral, Android as Central' combination the one that keeps me up at night. After many hours of fiddling, testing, googling and trying, I have very much pinned down the problem to this:
From the Android side, if I don't subscribe to the characteristic, a call to BluetoothGatt#writeCharacteristic(characteristic), like this:
String str = "the data";
xferCharacteristic.setValue(str.getBytes("UTF-8"));
mGatt.writeCharacteristic(xferCharacteristic);
will return 'true' and succeed, and the peripheralManager:didReceiveWriteRequests: callback will be called on the iOS side where I can manipulate the precious received data as I see fit. So far so good. But, if I try to update a characteristic from the iOS end, the Android central won't get notified (the callback BluetoothGattCallback#onCharacteristicChanged should be called, but it isn't), since it did not subscribe to the characteristic.
If I make the Android central subscribe to the characteristic offered by the iOS peripheral, by means of this section of code:
First, connect to the iOS peripheral with
public void onScanResult(int callbackType, ScanResult result) {
BluetoothDevice btDevice = result.getDevice();
mGatt = device.connectGatt(appContext, false, mGattCallback);
...
with mGattCallback an instance of BLEGattCallback which will handle the onServicesDiscovered callback:
public class BLEGattCallback extends BluetoothGattCallback {
private static final UUID CLIENT_CHARACTERISTIC_CONFIG_DESCRIPTOR_UUID = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb");
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
List<BluetoothGattService> services = gatt.getServices();
for(BluetoothGattService s : services) { // foreach service...
if(UUID.fromString(MyServiceUUID).equals(s.getUuid())) { // just the one I want...
List<BluetoothGattCharacteristic> characteristics = s.getCharacteristics();
for(BluetoothGattCharacteristic c : characteristics) { // foreach characteristic...
if(c.getUuid().toString().equals(BLEManager.FGUUIDXferQueueString)) { // just the char. I want...
c.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE);
for (BluetoothGattDescriptor descriptor : c.getDescriptors()) {
if(descriptor.getUuid().equals(CLIENT_CHARACTERISTIC_CONFIG_DESCRIPTOR_UUID)) {
descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
gatt.writeDescriptor(descriptor);
}
}
gatt.setCharacteristicNotification(c, true);
}
}
}
}
}
This makes the Android central correctly subscribe for the characteristic (the callback method peripheralManager:central:didSubscribeToCharacteristic: is called on the iOS peripheral), BUT, if i do this, the call to mGatt.writeCharacteristic(xferCharacteristic) will return 'false' and no data will be written to the peripheral, so it's a kind of can-only-write or can-only-notify-update situation.
I have unsuccessfully tried to find out the meaning of writeCharacteristic returning 'false', to no avail (seriously, an error code would help a lot).
I've tried a lot of different combinations, values, etc... but, bottom line: as soon as I call gatt.writeDescriptor subsequent calls to writeCharacteristic will fail, and if I don't call gatt.writeDescriptor the android central won't subscribe.
I'm pretty much stuck here. Any help appreciated. Thanks a lot.
Classic issue. You must wait for the operation to complete before you can issue another one. See Android BLE BluetoothGatt.writeDescriptor() return sometimes false.
Thanks to the received hint, this issue has been solved. These are the changes I made to the code:
The Android client must wait for the writeDescriptor(...) request to finish before issuing a writeCharacteristic(...) command. For that, I had to #Override the method onDescriptorWrite on my BLEGattCallback class, which will be called when the writeDescriptor operation completes. I moved my first writeCharacteristic(...) call here, and now the information is sent to the iOS endpoint (the rest must be flow-controlled). So I'm very happy.
Related
I am attempting to have my Ethereum smart contract connect to an external HTTP endpoint using Chainlink. Following along with Chainlink's documentation (https://docs.chain.link/docs/advanced-tutorial/) I deployed this contract onto the Rinkeby testnet.
pragma solidity ^0.8.7;
import "github.com/smartcontractkit/chainlink/blob/develop/contracts/src/v0.8/ChainlinkClient.sol";
// MyContract inherits the ChainlinkClient contract to gain the
// functionality of creating Chainlink requests
contract getHTTP is ChainlinkClient {
using Chainlink for Chainlink.Request;
bytes32 private thisDoesNotWork;
address private owner;
address private ORACLE_ADDRESS = 0x718Cc73722a2621De5F2f0Cb47A5180875f62D60;
bytes32 private JOBID = stringToBytes32("86b489ec4d84439c96181a8df7b22223");
string private url = "<myHTTPAddressAsString>";
// This endpoint URL is hard coded in my contract, and stored as a string (as in the example code).
// I control it and can have it reply with whatever I want, which might be an issue, returning data in a format that the oracle rejects
uint256 constant private ORACLE_PAYMENT = 100000000000000000;
constructor() public {
// Set the address for the LINK token for the network
setPublicChainlinkToken();
owner = msg.sender;
}
function requestBytes()
public
onlyOwner
{
Chainlink.Request memory req = buildChainlinkRequest(JOBID, address(this), this.fulfill.selector);
req.add("get", url);
sendChainlinkRequestTo(ORACLE_ADDRESS, req, ORACLE_PAYMENT);
}
function fulfill(bytes32 _requestId, bytes32 recVal)
public
recordChainlinkFulfillment(_requestId)
{
thisDoesNotWork = recVal;
}
function cancelRequest(
bytes32 _requestId,
uint256 _payment,
bytes4 _callbackFunctionId,
uint256 _expiration
)
public
onlyOwner
{
cancelChainlinkRequest(_requestId, _payment, _callbackFunctionId, _expiration);
}
// withdrawLink allows the owner to withdraw any extra LINK on the contract
function withdrawLink()
public
onlyOwner
{
LinkTokenInterface link = LinkTokenInterface(chainlinkTokenAddress());
require(link.transfer(msg.sender, link.balanceOf(address(this))), "Unable to transfer");
}
modifier onlyOwner() {
require(msg.sender == owner);
_;
}
// A helper funciton to make the string a bytes32
function stringToBytes32(string memory source) private pure returns (bytes32 result) {
bytes memory tempEmptyStringTest = bytes(source);
if (tempEmptyStringTest.length == 0) {
return 0x0;
}
assembly { // solhint-disable-line no-inline-assembly
result := mload(add(source, 32))
}
}
}
I found a node on the Chainlink market (https://market.link/jobs/529c7194-c665-4b30-8d25-5321ea49d9cc) that is currently active on rinkeby (according to Etherscan it has been active within the past 3 days and presumably still working).
I deploy the contract and fund the contract with LINK. I call the requestBytes() function through remix and everything works as expected. Metamask pays the gas, the LINK is removed from my contract, I get a transaction hash, and no errors.
However, my endpoint never logs a request attempt, the oracle never lists a transaction on its Etherscan page, and my data is not present.
I have attempted to use other jobs from the Chainlink market with similar outcomes.
I have also attempted to use other HTTP endpoints, like the ones from the Chainlink examples, with similar outcomes, however I doubt this is the issue, since it appears the HTTP request is never even getting called (as referenced by the fact that my HTTP endpoint does not log the request)
Without an error message, and being new to Web3 dev, I am not sure where to start debugging. I found this comment on Github: https://github.com/smartcontractkit/documentation/issues/513 and implemented the suggestion here without luck.
I also found this: Chainlink - Job not being fulfilled but this was not helpful either.
My current considerations for where the error might be:
The oracles are whitelisted and reject my request outright. Have considered creating my own node but want to avoid if possible at this stage.
I have an type error in how I am formatting the request in my contract, like the example in the GitHub exchange I found and referenced above.
EDIT: I am also open to other options beyond Chainlink to connect my contract to an HTTP GET endpoint, if anyone has any suggestions. Thanks!
I've been working on something similar recently and would suggest you try using the kovan network and the oracle that chainlink has there. Even more specifically, I think it would be a good idea to confirm you can get it working using the api, oracle, and jobid listed in the example on that page you are following... here:
https://docs.chain.link/docs/advanced-tutorial/#contract-example
Once you get that example working, then you can modify it for your usage. The jobid in that tutorial is for returning a (multiplied) uint256... which, for your API, I think is not what you want as you are wanting bytes32 it sounds like... so when you try to use it with your API that returns bytes32 the jobid would be: 7401f318127148a894c00c292e486ffd as seen here:
https://docs.chain.link/docs/decentralized-oracles-ethereum-mainnet/
Another thing that might be your issue, is your api. You say you control what it returns... I think it might have to return a response in bytes format, like Patrick says in his response (and his comments on his response) here:
Get a string from any API using Chainlink Large Response Example
Hope this is helpful. If you cannot get the example in the chainlink docs to work, let me know.
I´m getting this error when procedure NotificationsRegistrationHandler is executed at application startup.
java.lang.IllegalStateException: Object NotificationsRegistrationHandler only supports OFFLINE but is being called via RemoteApplicationServer
As documentation says:
If you have a completely offline application and you need this Registration Handler procedure to be generated offline exclusively, set Main property = False and Connectivity Support property = Offline
I have set my main SD object Registration Handler property to use this procedure.
I have also set the following properties on procedure NotificationsRegistrationHandler:
What it´s wrong with my code or configuration?
Thanks,
Rogelio Arosemena
Rogelio,
I think that this may be an issue with offline mode. We can check it out.
In the meantime, you could set to Connectivity Support = Online and this should fix your issue.
I found an alternative solution by creating an external object on Android to return One Signal Id. The code was:
OneSignal.idsAvailable(new OneSignal.IdsAvailableHandler() {
#Override
public void idsAvailable(String userId, String registrationId) {
try{
return userId;
}catch(Exception e){
e.printStackTrace();
return "";
}
}
});
Device registration on One Signal was ok on SD application. The problem was that procedure NotificationRegistrationHandler was never executed (offline or online), so we can't store DeviceToken on our table.
We will have to do the same for IOS with this code:
OSPermissionSubscriptionState status = OneSignal.getPermissionSubscriptionState();
status.getSubscriptionStatus().getUserId();
my scenario is that me as a movie distributor, need to update my clients on new movies, I publish this information on a topic with durable subscribers and clients who want to buy the movie will express their interest.
However, this is where things go south, my implementation of the publisher stops listening as soon as it receives the first reply. Any help would be greatly appreciated. Thank you.
request(Message message)
Sends a request and waits for a reply.
The temporary topic is used for the JMSReplyTo destination; the first reply is returned, and any following replies are discarded.
https://docs.oracle.com/javaee/6/api/javax/jms/TopicRequestor.html
First thing first... I have questions regarding the scenario. Is this some kind of test/exercice, or are we talking about a real world scenario ?
Are all client interested in the movie SEPARATE topic subscribers ? How does that scale ? I the plan to have a topic for every movie, and possible interested parties declaring durable subscribers (one each, for every movie) ? This seems to be abuse of durable subcribers... I would suggest using ONLY one subscriber (in system B) to a "Movie Released" event/topic (from system A), and have some code (in system B) reading all the clients from a DB to send emails/messages/whatever. (If system A and B are the same, it may or not be a good idea to use EMS at all... depends.)
If it is not an exercise, I must comment : Don't use a MOM (EMS, ActiveMQ) to do a DBMS' (Oracle, PostGreSQL) work !
With the disclaimer section done, I suggest an asynchronous subscription approach (These two clips are taken for the EMS sample directory. File tibjmsAsyncMsgConsumer.java).
Extract from the constructor (The main class must implements ExceptionListener, MessageListener):
ConnectionFactory factory = new com.tibco.tibjms.TibjmsConnectionFactory(serverUrl);
/* create the connection */
connection = factory.createConnection(userName,password);
/* create the session */
session = connection.createSession();
/* set the exception listener */
connection.setExceptionListener(this);
/* create the destination */
if (useTopic)
destination = session.createTopic(name);
else
destination = session.createQueue(name);
System.err.println("Subscribing to destination: "+name);
/* create the consumer */
msgConsumer = session.createConsumer(destination);
/* set the message listener */
msgConsumer.setMessageListener(this);
/* start the connection */
connection.start();
The method is then called every time a message arrives.
public void onMessage(Message msg)
{
try
{
System.err.println("Received message: " + msg);
}
catch (Exception e)
{
System.err.println("Unexpected exception in the message callback!");
e.printStackTrace();
System.exit(-1);
}
}
You want to continue reading messages in a loop. Here is an example:
/* read messages */
while (true)
{
/* receive the message */
msg = msgConsumer.receive();
if (msg == null)
break;
if (ackMode == Session.CLIENT_ACKNOWLEDGE ||
ackMode == Tibjms.EXPLICIT_CLIENT_ACKNOWLEDGE ||
ackMode == Tibjms.EXPLICIT_CLIENT_DUPS_OK_ACKNOWLEDGE)
{
msg.acknowledge();
}
System.err.println("Received message: "+ msg);
}
You may want to also consider a possible issue with durable consumers. If your consumers never pick up their messages, storage will continue to grow at the server side. For this reason you may want to send your messages with an a expiration time, and/or limit maximum number of messages (or size in KB/MB/GB) of the JMS topics you are using.
I have a Swift project that's using AVCaptureSession to take photos within the app. I'm having difficulty getting the right syntax to properly clean up my objects. In Obj-C the suggested code would be as follows;
// Releases the object - used for late session cleanup
static void capture_cleanup(void* p)
{
NewPostPreviewViewController* csc = (NewPostPreviewViewController*)p;
[csc release]; // releases capture session if dealloc is called
}
// Stops the capture - this stops the capture, and upon stopping completion releases self.
- (void)stopCapture {
// Retain self, it will be released in capture_cleanup. This is to ensure cleanup is done properly,
// without the object being released in the middle of it.
[self retain];
// Stop the session
[session stopRunning];
// Add cleanup code when dispatch queue end
dispatch_queue_t queue = dispatch_queue_create("VideoDataOutputQueue", NULL);
dispatch_set_context(queue, self);
dispatch_set_finalizer_f(queue, capture_cleanup);
[dataOutput setSampleBufferDelegate: self queue: queue];
dispatch_release(queue);
}
The finalizer would call capture_cleanup but I have no idea how to set the context or the pointer to the capture_cleanup function (or even what the function definition would look like)
So far I've tried the following but I'm not convinced I'm even on the right track;
let p: UnsafeMutablePointer<NewPostPreviewViewController> = UnsafeMutablePointer.alloc(sizeof(NewPostPreviewViewController))
p.initialize(self)
var videoDataOutputQueue = dispatch_queue_create("VideoDataOutputQueue", nil)
dispatch_set_context(videoDataOutputQueue, p)
dispatch_set_finalizer_f(videoDataOutputQueue, ????);
self.videoDataOutput!.setSampleBufferDelegate(self, queue: videoDataOutputQueue)
dispatch_release(videoDataOutputQueue)
Any help converting this would be most appreciated!
Solved using bridging to Objective-C code. By including a CameraController.m Objective-C class in my Swift project (with associated header) I bridge for access to the camera feed.
The Objective-C class does all the work I need, and stores the last image taken. It also produces a notification once the image is taken, allowing my Swift class to observe the notification and go get the last image taken.
I'm using PNaCl and I'm in a situation where first I receive a message that is handled in the 'HandleMessage' function as the normal way, but then in the current HandleMessage execution, I need to wait for a user input that would come from an other message in order to complete the execution.
I'm wondering if this is possible to do that (handling a message while already waiting in the 'HandleMessage' function) ? And if so, can someone give me a trick ?
Thanks !
HandleMessage is currently called on one thread, the main thread. So you cannot receive a message while you are handling another message.
We typically suggest you spawn a new thread to do your work, and leave the main thread to handle messages, and queue them for the new thread to handle. Take a look at the nacl_io_demo example in the SDK for an example of this technique (found in examples/demo/nacl_io).
Another solution is to use a state machine; i.e. keep track of your current state in a variable instead of on the stack.
For example:
enum State {
STATE_INIT,
STATE_WAITING_FOR_INPUT,
STATE_DO_OTHER_STUFF,
};
State state_;
virtual void HandleMessage(const pp::Var& var_message) {
switch (state_) {
case STATE_INIT:
if (var_message.AsString() == "first_message") {
state_ = STATE_WAITING_FOR_INPUT;
// Do some work before you need the user input ...
}
break;
case STATE_WAITING_FOR_INPUT:
if (var_message.AsString() == "user_input") {
// Do more work, now that we've received input from the user...
state_ = STATE_DO_OTHER_STUFF;
}
break;
}
}