UPGRADE YOUR SKILLS: Learn advanced Swift and SwiftUI on Hacking with Swift+! >>

WebSockets client on Swift does not receive all message data

Forums > Swift

Hi all! I've posted that question on StackOverflow but it hasn't received much attention, hence posting here 🙂

I'm trying to receive financial data from the following WebSockets API: wss://api.qtrade.io/v1/ws.

I tried it in Swift using the following code in a playground:

import Foundation

let urlSession = URLSession(configuration: .default)
let url = URL(string: "wss://api.qtrade.io/v1/ws")!
let webSocketTask = urlSession.webSocketTask(with: url)

let message = URLSessionWebSocketTask.Message.string("{\"method\": \"subscribe\", \"channel\": \"market_49\", \"nonce\": \"HXPAxAWn\"}")

webSocketTask.send(message) { error in
    if let error = error {
        print("WebSocket sending error: \(error)")
    }
}

webSocketTask.receive { result in
    switch result {
    case .failure(let error):
        print("Failed to receive message: \(error)")
    case .success(let message):
        switch message {
        case .string(let text):
            print("Received text message: \(text)")
        case .data(let data):
            print("Received binary message: \(data)")
        @unknown default:
            fatalError()
        }
    }
}

webSocketTask.resume()

I correctly receive data, i.e. I get in the conditional path of "Received text message", but the response is not complete. I already checked that it's not only the printed output which is truncated, but really the message itself that is not complete (see the full program output here).

I also tried connecting to this API in Python with the somewhat equivalent code:

import asyncio
import random
import string

import websockets

async def hello():
    uri = "wss://api.qtrade.io/v1/ws"
    async with websockets.connect(uri) as websocket:

        await websocket.send('{"method": "subscribe", "channel": "market_49", "nonce": "HXPAxAWn"}')
        print(f"Sent request")

        response = await websocket.recv()
        print(f"Received: {response}")

asyncio.get_event_loop().run_until_complete(hello())

In that case, the response is complete (see the full program output here).


What am I missing to get the complete API response with my Swift call? Does it have to do with the fact that the receive closure is called only once because I didn't re-register it (but in Python it's also called only once…) and if yes, how would I fix it?

Thanks in advance for any help! 🙏

4      

Hacking with Swift is sponsored by RevenueCat

SPONSORED Take the pain out of configuring and testing your paywalls. RevenueCat's Paywalls allow you to remotely configure your entire paywall view without any code changes or app updates.

Learn more here

Sponsor Hacking with Swift and reach the world's largest Swift community!

Archived topic

This topic has been closed due to inactivity, so you can't reply. Please create a new topic if you need to.

All interactions here are governed by our code of conduct.

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.