I've been messing around trying to create a backend for an IOS game using WebSockets (with the ws library for node.js). So I've figured out the basics of the ws library (ws.on listeners, ws.send etc. and I'm able to send a basic echo message using echo). However, I tried to store each ws connection in a "Player" object, so it would be easily accessible by having a function in the websocket server class like:
sendMyMessage(ws) {
ws.send("Message")
}
and calling:
WebSocketServerInstance.sendMyMessage(PlayerInstance.ws)
Maybe not with that exact syntax, but you get the idea... Since a ws connection is an object itself (so, presumably a reference type, not a value type), this should work so long as I call sendMyMessage() on the same WebSocketServer instance that received the connection, right? Or am I missing something critical / not approaching this in the right way?
When I do something like this, my IOS debugger doesn't receive anything (however if I console.log the ws object in the sendMyMessage() function in Node, it does in fact output what I am assuming is the correct ws object), but it works with all the other more basic functions I described above, like sending a message back using a "ws.on('message, ...) listener.
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I'm coding a script that connects to the Binance websocket and uses the .run_forever() method to constantly get live data from the site. I want to be able to debug my code and watch the values of variables as the change but I'm not sure how to do this as the script basically hangs on the line with the .run_forever() method, because it is an infinite event loop. This is by design as I want to continuously get live data (it receives a message approximately every second), but I can't think of a way a good way to debug it.
I'm using VSCode and here are some snippets of my code to help understand my issue. The message function for the websocket is just a bunch of technical analysis and trade logic, but it is also the function that contains all the changing variables that I want to watch.
socket = f"wss://stream.binance.com:9443/ws/{Symbol}#kline_{interval}"
def on_open(ws):
print("open connection")
def on_message(ws, message):
global trade_list
global in_position
json_message = json.loads(message)
candle = json_message['k'] # Accesses candle data
...[trade logic code here]...
def on_close(ws):
print("Websocket connection close")
# ------------------------- Define a websocket object ------------------------ #
ws = websocket.WebSocketApp(socket, on_open=on_open, on_message=on_message, on_close=on_close)
ws.run_forever()
If more code is required to answer the question, then I can edit this question to include it (I'm thinking if you would like to have an idea of what variables I want to look at, I just thought it would be easier and simpler to show these parts).
Also, I know using global isn't great, once I've finished (or am close to finishing) the script, I want to go and tidy it up, I'll deal with it then.
I'm a little late to the party but the statement
websocket.enableTrace(True)
worked for me. Place it just before you define your websocket object and it will print all traffic in and out of the websocket including any exceptions that you might get as you process the messages.
I am trying to implement a pub/sub broker with ZeroMQ where it is possible to restrict clients from subscribing to prefixes they are not allowed to subscribe to. I found a tutorial that tries to achieve a similar thing using the ZMQ_XPUB_MANUAL option. With zeromq.js it is possible to set this option:
import * as zmq from "zeromq";
// ...
const socket = new zmq.XPublisher({ manual: true });
After setting this option I am able to receive the subscription messages by calling .receive() on this socket:
const [msg] = await socket.receive();
But I have no Idea how to accept this subscription. Usally this is done by calling setSockOpt with ZMQ_SUBSCRIBE but I don't know how to do this with zeromq.js.
Is there a way to call setSockOpt with zeromq.js or is there another way to accept a subscription?
Edit
I tried user3666197's suggestion to call setSockOpt directly, but I am not sure how to do this. Rather than doing that, I took another look in the sources and found this: https://github.com/zeromq/zeromq.js/blob/master/src/native.ts#L617
It seems like setSockOpt is exposed to the TypeScript side as protected methods of the Socket class. To try this out, I created my own class that inherits XPublisher and exposed an acceptSubscription message:
class CustomPublisher extends zmq.XPublisher {
constructor(options?: zmq.SocketOptions<zmq.XPublisher>) {
super(options);
}
public acceptSubscription(subscription: string | null): void {
// ZMQ_SUBSCRIBE has a value of 6
// reference:
// https://github.com/zeromq/libzmq/blob/master/include/zmq.h#L310
this.setStringOption(6, subscription);
}
}
This works like a charm! But do not forget to strip the first byte of the subscription messages, otherwise your client won't receive any messages since the prefix won't match.
Q : "Is there a way to call setSockOpt() with zeromq.js or is there another way to accept a subscription?"
So, let me first mention Somdoron to be, out of doubts & for ages, a master of the ZeroMQ tooling.
Next comes the issue. The GitHub-sources, I was able to review atm, seem to me, that permit the ZMQ_XPUB-Socket-archetypes to process the native API ZMQ_XPUB_MANUAL settings ( re-dressed into manual-property, an idiomatic shift ), yet present no method (so far visible for me) to actually permit user to meet the native API explicit protocol of:
ZMQ_XPUB_MANUAL: change the subscription handling to manual...with manual mode subscription requests are not added to the subscription list. To add subscription the user need to call setsockopt() with ZMQ_SUBSCRIBE on XPUB socket./__ from ZeroMQ native API v.4.3.2 documentation __/
Trying to blind-call the Socket-inherited .SetSockOpt() method may prove me wrong, yet if successful, it may be a way to inject the { ZMQ_SUBSCRIBE | ZMQ_UNSUBSCRIBE } subscription-management steps into the XPUB-instance currently having been switched into the ZMQ_XPUB_MANUAL-mode.
Please test it, and if it fails to work via this super-class inherited method, the shortest remedy would be to claim that collision/conceptual-shortcomings directly to the zeromq.js maintainers ( it might be a W.I.P. item, deeper in their actual v6+ refactoring backlog, so my fingers are crossed for either case ).
TL;DR below.
I am currently developing a React/Redux SPA that is driven by real-time data. I've decided to use ws, instead of socket.io since socket.io feels a bit high level for what I'm doing, I'd rather manage sockets myself.
In saying that, I'm struggling to find a way to manage the separation of updates/messages per view/route. Since I'm using client-side routing it's per express route won't really work...
Messages between the server and client via WebSockets are JSON with actions like GET_ITEMS then a response of GET_ITEMS_SUCCESS with an array of 'items' and for errors: ..._ERROR etc. This is all fine, since it's just 1 to 1 transaction. Though the problem arises when broadcasting (1 to all) to all relevant clients when the server receives an update.
So, I assume it best practice to limit these broadcasts to the clients that are viewing/want the data. So when viewing, for example, the Item page, there is no point in broadcasting updates to the User data since that is only used on the User page.
I haven't been able to find any common practices when dealing with this sort of situation, just a few small outdated/barely used wrappers for ws that just add a few basic functions to leave/join but don't offer much flexibility with implementation.
What I think MIGHT work is to have an object/array for each 'group'/'room', which stores the clients that are currently listening to updates from a given section. So a user would send an action to INIT_LISTEN (& ``) with a param of category, e.g. ITEM for updates and other actions related to items.
TL;DR
What my question really boils down to is: How do I store a reference to a single socket? (ws client object? ws client ID?) Then, can I store this in an object/array to iterate through like below.
const ClientRooms = {
Items: {
{
...ws
}
/* ...rest of the client */
}
}
or
const ClientRooms = {
Items: [ "xyz" ] /* Array of ws ids */
}
I have a "ping--pong" heartbeat function to keep clients active and prevent silent connection failures/disconnections. I can't find if ws.terminate() still fires the ws close event so I can iterate 'group'/'room' the object/array to find and remove instances of that client.
I am working on an AS3 project in FDT6. I am using the lastest FLEX 4.6 and AIR 3.7.
I have a worker.swf file that is embedded into the main application to do threading work with.
I am using the MessageChannel class to pass information between the two.
In my main class I have defined
private var mainToWorker:MessageChannel;
private var workerToMain:MessageChannel;
mainToWorker = Worker.current.createMessageChannel(worker);
workerToMain = worker.createMessageChannel(Worker.current);
on the mainToWorker I only ever send messages. In these messages I send a byte array of information. The information is an object that contains a 'command' property and a 'props' property. Basically acting like a function call. The command is a function name and the props is an object that contains data for that function.
mainToWorkerMutex.lock();
mainToWorker.send(ByteArrayUtils.ObjectToByteArray({command:"DoSomething", props:{propA:1,propB:7}}));
mainToWorkerMutex.unlock();
The same occurs for the workerToMain var except I only send byte data that contains the 'message' and 'props' parameters.
workerToMainMutex.lock();
workerToMain.send(ByteArrayUtils.ObjectToByteArray({command:"complete", props:{return:"result"}}));
workerToMainMutex.unlock();
As a sanity check I make sure that the message channels are getting what they should.
It is working fine when I build it in FDT, however when it is built using an ANT script through flash builder I am sometimes getting the 'command' events coming back through in the workerToMain channel.
I am sending quite a lot of data through the message channel. Is it possible that I am overloading it and causing a buffer overflow into the other message channel somehow? How could that only be happening in FB?
I have checked my code many times and I am sure there is nothing in my own code that is sending that message back.
I had similar issue. When sending many bytearrays using channels sometimes things i received was not things i've actually sended. I had 4 channels (message channel to worker, message channel to main, data channel to worker, data channel to main).
I've noticed that data channel to main was affecting message channel to worker. When i turned off data channel to main - message channel to worker stared working just fine :D...
They have a big issue there with sending byte arrays it seems.
But what helped me was using shareable (at first it was not shareable) bytearray for communication via channels, but only for communication, as soon as i am receiving such bytearray i'm copying it to another byte array and parsing a copy.
This removed the problem (made quite hard stress tests there)...
Cheers
P.S. I'm also using static functions (like your ByteArrayUtils) to create bytearray's used for communication, but it seems fine, even made tests using non static functions.
So, it looks like I have found the issue. Looks like it's the ByteArray that is doing it.
ByteArray.toString() is basically sometimes mangles your data meaning you can't really trust it.
http://www.actionscript.org/forums/showthread.php3?t=155067
If you read the comment by "Jim Freer" he mentions how strings sometimes do this.
My solution was to switch to using a JSON encoded string instead of ByteArray data in the message channel. The reason I was using bytearray data to begin with is because I wanted to preserve class definition information, which JSON doesn't do.
In express you call var app = module.exports = express.createServer(); which creates a new HTTPServer object. I'd like to get access to the current req object from this app(HTTPServer) object. Is there a way to do this?
The req object is only created when the underlying HTTPServer actually gets a request, and only lasts for as long as the request is processed. So it's not really meaningful to talk about it outside the context of a callback.
During a callback, you can simply copy the appropriate data from the session object somewhere else and use that copy in your websockets code. But you can't count on the request object, or even the session object, remaining after you've finished processing the request.
Showing a small code example would be helpful; it sounds like you've got an "XY problem" (you want to accomplish a goal X and you've decided that technique Y is the right way to do it, when in fact technique Z might work better).