WebSocket Swift iOS macOS: Starscream and URLSession |…

WebSocket Libraries for Swift (iOS/macOS): Starscream and URLSessionWebSocketTask

WebSocket is a protocol that provides full-duplex communication between a client and a server over a single TCP connection. In the Swift ecosystem (iOS/macOS), there are two main approaches for working with WebSocket: the native implementation URLSessionWebSocketTask (available since iOS 13/macOS 10.15) and the popular third-party library Starscream. Both allow you to create reactive real-time applications: chats, ticker feeds, multiplayer games, etc.

Native Implementation URLSessionWebSocketTask

With the release of iOS 13, Apple added built-in WebSocket support to the Foundation framework. This eliminates the need to add third-party dependencies if your application targets modern OS versions.

Key Features:

Fully asynchronous operation via async/await or callbacks
Automatic connection lifecycle management
Support for closeCode, closeReason for proper termination
Built-in integration with URLSession (timeout support, caching policies)

Example of connecting and sending a message:

import Foundation

class WebSocketManager {    private var webSocketTask: URLSessionWebSocketTask?    private let session = URLSession.shared        func connect() {        guard let url = URL(string: "wss://echo.websocket.org") else { return }        webSocketTask = session.webSocketTask(with: url)        webSocketTask?.resume()        receiveMessage()    }        func sendMessage(_ text: String) {        let message = URLSessionWebSocketTask.Message.string(text)        webSocketTask?.send(message) { error in            if let error = error {                print("Send error: \\(error.localizedDescription)")            }        }    }        private func receiveMessage() {        webSocketTask?.receive { [weak self] result in            switch result {            case .success(let message):                switch message {                case .string(let text):                    print("Received: \\(text)")                case .data(let data):                    print("Received binary data: \\(data)")                @unknown default:                    fatalError()                }                // Continue listening                self?.receiveMessage()            case .failure(let error):                print("Receive error: \\(error)")                // Possibly reconnect            }        }    }        func disconnect() {        webSocketTask?.cancel(with: .normalClosure, reason: nil)    }}

Starscream — Flexible and Proven Library

Starscream is an open-source WebSocket library for Swift, written by Dalton Cherry and maintained by the community. It works on iOS, macOS, tvOS, and watchOS, starting from older versions (iOS 8+). Starscream provides more control over the connection and supports additional features such as compression (permessage-deflate) and custom headers.

Installation via Swift Package Manager:

// In Package.swift or via Xcode: File → Swift Packages → Add Package Dependency.package(url: "https://github.com/daltoniam/Starscream.git", from: "4.0.0")

Key Features:

Support for WebSocketDelegate for all events (connection, data reception, errors, disconnection)
Manual ping/pong management to maintain the connection
Ability to send binary data (Data) and strings (String/UTF-8)
Support for SSL/TLS and self-signed certificates