We need to talk about Websockets

If you're tired of slow and flaky networking, this talk will explain to you the state-of-the-art solution: Websockets. Using technologies such as Apple's freshly announced URLSession Websockets, incredible new open-source SwiftNIO, and Network.framework, we'll look at how you can open a two-way socket between your app and server to accelerate your networking, allowing you to communicate without disruptions, do so securely, and even learn some tips and tricks from Apple. The speaker is the maintainer of Starscream, one of the most popular Swift Websocket libraries.

Transcript

1. Kristaps Grinbergs We need to talk about WebSockets fassko
2. About me Swift developer Open source Swift Weekly Brief
3. Mr. Byte
4. Plan What are WebSockets How to use with  platforms Demo Pros and Cons
6. Using WebSockets Chat apps ⏳ Real time notifications Stock market Multiplayer games ⚽ Sport scores
7. History
8. Long Polling
9. “Innovation is taking two things that already exist and putting them together in a new way.” - Tom Freston
10. History 2008 Michael Carter and Ian Hickson 2010 RFC 6455 2013 iOS and Android
11. - Wikipedia WebSocket is a computer communications protocol, providing full-duplex communication channels over a single TCP connection.
12. What are WebSockets? ✌ Two-way, single connection Persistent Low latency
14. RFC 6455 standard https://tools.ietf.org/html/rfc6455
15. How does it work?
16. Connection handshake GET Request GET /chat HTTP/1.1 Host: example.com Upgrade: websocket Connection: Upgrade Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ== Sec-WebSocket-Version: 13 Sec-WebSocket-Protocol: chat, superchat Origin: http://example.com Response HTTP/1.1 101 Switching Protocols Upgrade: websocket Connection: Upgrade Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo= Sec-WebSocket-Prototocol: chat
19. Frames
20. Control byte
21. OpCode
22. Mask
23. Payload length
24. Masking key
25. Payload data
26. PING PONG
29. Before iOS 12 CFNetwork Third party dependancies
31. Starscream Written in Swift WebSocket (RFC 6455) Open source on Github
32. Starscream initialize let url = URL(string: "http://localhost:8080")! var request = URLRequest(url: url) socket = WebSocket(request: request) socket.delegate = self socket.connect()
33. Starscream receive func didReceive(event: WebSocketEvent, client: WebSocket) { } switch event { case .connected(let headers): isConnected = true print("websocket is connected: \(headers)") case .disconnected(let reason, let code): isConnected = false print("websocket is disconnected: \(reason) with code: \(code)") case .text(let string): print("Received text: \(string)") case .binary(let data): print("Received data: \(data.count)") case .ping(_): break case .pong(_): break case .cancelled: isConnected = false case .error(let error): isConnected = false handleError(error) }
34. Starscream send socket.write(string: "Hello") { print("Message sent") }
35. Starscream ping/pong socket.respondToPingWithPong = true socket.write(ping: "PING")
36. Starscream close socket.disconnect(closeCode: CloseCode.goingAway.rawValue)
37. Network.framework iOS 13.0+  Lower level
38. Network.framework initialize let connection = NWConnection(host: .init("echo.websocket.org"), port: .https, using: .tls) let queue = DispatchQueue(label: "com.network.framework") connection.start(queue: queue)
39. Network.framework send let message = "Hello".data(using: .utf8)! connection.send(content: message, completion: .contentProcessed { error in if let error = error { print("can't process message \(error)") } })
40. Network.framework receive connection.receiveMessage { data, messageContext, isComplete, error in if let error = error { print("Failed to receive message \(error)") } else if let data = data, isComplete { print(String(data: data, encoding: .utf8)!) } } connection.receive(minimumIncompleteLength: 2, maximumLength: 4096) { data, context, isComplete, error in if let error = error { print("error", error) } else if let data = data { print("received: ", String(data: data, encoding: .utf8)!) } if isComplete, context == nil, error == nil { print("END") } }
41. Network.framework close connection.cancel()
42. URLSessionWebSocketTask iOS 13.0+  URLSession
43. URLSessionWebSocketTask Initialize let session = URLSession(configuration: .default) let url = URL(string: "wss://echo.websocket.org")! let webSocketTask = session.webSocketTask(with: url) webSocketTask.resume()
44. URLSessionWebSocketTask Send webSocketTask.send(.string("Hello")) { error in if let error = error { print("Can't send message \(error)") } }
45. URLSessionWebSocketTask Receive webSocketTask.receive { result in switch result { case .success(let message): switch message { case .data(let data): print("Data received: \(data)") case .string(let text): print("Text received: \(text)") } case .failure(let error): print("Error in receiving \(error)") } }
46. URLSessionWebSocketTask PING/PONG webSocketTask.sendPing { error in if let error = error { print("PONG not received \(error)") } }
47. URLSessionWebSocketTask Close webSocketTask.cancel(with: .goingAway, reason: nil)
49. SwiftNIO  Cross-platform ✨ Async event driven Network framework
50. NIOWebSocket ➿ Based on event loops Low level Full control
51. NIO Transport Services SwiftNIO for  platforms Based on Network.framework Low level
52. On top of SwiftNIO Written in Swift Modular
53. Client & Server On SwiftNIO Medium level
54. Client _ = try promise.futureResult.wait() var eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: 2) let port: Int = 8709 let promise = eventLoopGroup.next().makePromise(of: String.self) WebSocket.connect(to: "ws://localhost:\(port)", on: eventLoopGroup) { ws in ws.send("hello") ws.onText { ws, string in print(string) } }.cascadeFailure(to: promise)
55. Server let upgradePipelineHandler: (Channel, HTTPRequestHead) -> EventLoopFuture<Void> = { channel, req in WebSocket.server(on: channel) { ws in } } ws.onText { ws, string in print("received") ws.send(string.trimmingCharacters(in: .whitespacesAndNewlines).reversed()) } ws.onBinary { ws, buffer in print(buffer) } ws.onClose.whenSuccess { value in print("onClose") }
56. var eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: 2) let port = Int.random(in: 8000..<9000) let promise = eventLoopGroup.next().makePromise(of: String.self) let server = try ServerBootstrap(group: eventLoopGroup).childChannelInitializer { channel in let webSocket = NIOWebSocketServerUpgrader( shouldUpgrade: { channel, req in return channel.eventLoop.makeSucceededFuture([:]) }, upgradePipelineHandler: upgradePipelineHandler ) return channel.pipeline.configureHTTPServerPipeline( withServerUpgrade: ( upgraders: [webSocket], completionHandler: { ctx in // complete }) ) }.bind(host: "localhost", port: port).wait() _ = try promise.futureResult.wait() try server.close(mode: .all).wait() Server
57. Vapor WebSockets client let websocket = WebSocket.connect(to: url, on: app.eventLoopGroup) { ws in ws.onText { ws, text in print(text) } ws.send("Hello") }
58. func routes(_ app: Application) throws { app.webSocket("") { request, ws in } } Vapor WebSockets server ws.send("You have been connected to WebSockets") ws.onText { ws, string in ws.send(string.trimmingCharacters(in: .whitespacesAndNewlines).reversed()) } ws.onClose.whenComplete { result in switch result { case .success(): print("Closed") case .failure(let error): print("Failed to close connection \(error)") } }
59. Server on iOS Starscream NIO Transport Services Network.framework
60. Starscream URLWebSocketTask?
62. Demo
64. Tools Charles Proxy Proxyman Cleora websocat
66. Pros Realtime updates Faster apps Supported by  * * iOS 13.0+
67. Cons Before iOS13 can be buggy ⛓ Long polling can be more reliable ⚔ Tricky to debug Closing connection
68. swiftwebsockets.com
69. fassko www.kristaps.me