Socket.IO

Real-time bidirectional communication with Socket.IO ↗ for Skip apps on both iOS and Android.

About

SkipSocketIO wraps the native Socket.IO client libraries for each platform:

iOS/macOS: socket.io-client-swift ↗ (v16+)
Android: socket.io-client-java ↗ (v2.1)

Key features inherited from Socket.IO:

Automatic reconnection with exponential backoff
Packet buffering and automatic acknowledgments
Event-driven communication with emit and on
Multiplexing through namespaces
Transport fallback (WebSocket with HTTP long-polling fallback)

Setup

Add the dependency to your Package.swift file:

let package = Package(
    name: "my-package",
    products: [
        .library(name: "MyProduct", targets: ["MyTarget"]),
    ],
    dependencies: [
        .package(url: "https://source.skip.dev/skip-socketio.git", "0.0.0"..<"2.0.0"),
    ],
    targets: [
        .target(name: "MyTarget", dependencies: [
            .product(name: "SkipSocketIO", package: "skip-socketio")
        ])
    ]
)

Usage

Connecting to a Server

Create a client and connect:

import SkipSocketIO

let socket = SkipSocketIOClient(socketURL: URL(string: "https://example.org")!, options: [
    .secure(true),
    .reconnects(true),
    .reconnectAttempts(5),
])

socket.on(SocketIOEvent.connect) { _ in
    print("Connected! Socket ID: \(socket.socketId ?? "unknown")")
}

socket.on(SocketIOEvent.disconnect) { _ in
    print("Disconnected")
}

socket.on(SocketIOEvent.connectError) { data in
    print("Connection error: \(data)")
}

socket.connect()

Listening for Events

Use on for persistent listeners, or once for one-time handlers:

// Called every time the event fires
socket.on("chat message") { data in
    if let message = data.first as? String {
        print("Received: \(message)")
    }
}

// Called once, then automatically removed
socket.once("welcome") { data in
    print("Server welcome: \(data)")
}

Removing Event Handlers

// Remove handlers for a specific event
socket.off("chat message")

// Remove all handlers
socket.removeAllHandlers()

Catch-All Handler

Listen for every incoming event:

socket.onAny { eventName, data in
    print("Event '\(eventName)' received with data: \(data)")
}

Emitting Events

Send events with data to the server:

// Simple string
socket.emit("chat message", ["Hello, world!"])

// Multiple items of different types
socket.emit("update", ["status", 42, true])

// With a send completion callback
socket.emit("save", ["data to save"]) {
    print("Event sent")
}

Acknowledgements

Emit an event and receive an acknowledgement from the server:

socket.emitWithAck("get-users", ["room-1"]) { ackData in
    print("Server responded with: \(ackData)")
}

Connection Status

Check the current connection state:

if socket.isConnected {
    print("Socket ID: \(socket.socketId ?? "")")
}

switch socket.status {
case .connected:    print("Connected")
case .connecting:   print("Connecting...")
case .disconnected: print("Disconnected")
case .notConnected: print("Never connected")
}

Connect with Timeout

socket.connect(timeoutAfter: 5.0) {
    print("Connection timed out after 5 seconds")
}

Namespaces

Use SkipSocketIOManager to connect to multiple namespaces on the same server:

let manager = SkipSocketIOManager(socketURL: URL(string: "https://example.org")!, options: [
    .reconnects(true),
    .forceWebsockets(true),
])

let defaultSocket = manager.defaultSocket()
let chatSocket = manager.socket(forNamespace: "/chat")
let adminSocket = manager.socket(forNamespace: "/admin")

chatSocket.on("message") { data in
    print("Chat message: \(data)")
}

adminSocket.on("notification") { data in
    print("Admin notification: \(data)")
}

defaultSocket.connect()
chatSocket.connect()
adminSocket.connect()

Configuration Options

let socket = SkipSocketIOClient(socketURL: URL(string: "https://example.org")!, options: [
    // Transport
    .forceWebsockets(true),         // Use only WebSockets (no long-polling fallback)
    .forcePolling(true),            // Use only HTTP long-polling
    .compress,                      // Enable WebSocket compression
    .secure(true),                  // Use secure transports (wss://)
    .path("/custom-path/"),         // Custom Socket.IO server path

    // Reconnection
    .reconnects(true),              // Enable auto-reconnection
    .reconnectAttempts(10),         // Max reconnection attempts (-1 for infinite)
    .reconnectWait(1),              // Min seconds between reconnection attempts
    .reconnectWaitMax(30),          // Max seconds between reconnection attempts
    .randomizationFactor(0.5),      // Jitter factor for reconnection delay

    // Headers and parameters
    .extraHeaders(["Authorization": "Bearer token123"]),
    .connectParams(["userId": "abc"]),
    .auth(["token": "secret"]),

    // Other
    .forceNew(true),                // Always create a new engine
    .log(true),                     // Enable debug logging
    .selfSigned(true),              // Allow self-signed certificates (dev only)
    .enableSOCKSProxy(false),       // SOCKS proxy support
])

SwiftUI Integration

import SwiftUI
import SkipSocketIO

struct ChatView: View {
    @State var messages: [String] = []
    @State var inputText: String = ""
    @State var socket = SkipSocketIOClient(
        socketURL: URL(string: "https://chat.example.org")!,
        options: [.reconnects(true)]
    )

    var body: some View {
        VStack {
            List(messages, id: \.self) { message in
                Text(message)
            }
            HStack {
                TextField("Message", text: $inputText)
                    .textFieldStyle(.roundedBorder)
                Button("Send") {
                    socket.emit("chat message", [inputText])
                    inputText = ""
                }
            }
            .padding()
        }
        .task {
            socket.on("chat message") { data in
                if let msg = data.first as? String {
                    messages.append(msg)
                }
            }
            socket.connect()
        }
    }
}

API Reference

SkipSocketIOClient

The primary interface for Socket.IO communication.

Method / Property	Description
`init(socketURL:options:)`	Create a client for the given server URL
`connect()`	Connect to the server
`connect(timeoutAfter:handler:)`	Connect with a timeout callback
`disconnect()`	Disconnect from the server
`isConnected: Bool`	Whether the client is currently connected
`socketId: String?`	The server-assigned session ID
`status: SocketIOStatus`	Current connection status
`on(_:callback:)`	Register a persistent event handler
`once(_:callback:)`	Register a one-time event handler
`off(_:)`	Remove all handlers for an event
`removeAllHandlers()`	Remove all event handlers
`onAny(_:)`	Register a catch-all handler for all incoming events
`emit(_:_:completion:)`	Emit an event with data
`emitWithAck(_:_:ackCallback:)`	Emit an event and receive a server acknowledgement

SkipSocketIOManager

Manages connections and namespaces for a server.

Method	Description
`init(socketURL:options:)`	Create a manager for the given server URL
`defaultSocket()`	Returns a client for the default namespace (`/`)
`socket(forNamespace:)`	Returns a client for the given namespace

SocketIOStatus

Case	Description
`.notConnected`	Has never been connected
`.connecting`	Connection in progress
`.connected`	Currently connected
`.disconnected`	Was connected, now disconnected

SocketIOEvent

Standard event name constants.

Constant	Value	Description
`SocketIOEvent.connect`	`"connect"`	Fired on successful connection
`SocketIOEvent.disconnect`	`"disconnect"`	Fired on disconnection
`SocketIOEvent.connectError`	`"connect_error"`	Fired on connection error

SkipSocketIOClientOption

Option	Description	Android Support
`.compress`	WebSocket compression	Ignored
`.connectParams([String: Any])`	GET parameters for the connect URL	Ignored
`.extraHeaders([String: String])`	Extra HTTP headers	Supported
`.forceNew(Bool)`	Always create a new engine	Supported
`.forcePolling(Bool)`	HTTP long-polling only	Supported
`.forceWebsockets(Bool)`	WebSockets only	Supported
`.enableSOCKSProxy(Bool)`	SOCKS proxy	Ignored
`.log(Bool)`	Debug logging	Ignored
`.path(String)`	Custom Socket.IO path	Supported
`.reconnects(Bool)`	Auto-reconnection	Supported
`.reconnectAttempts(Int)`	Max reconnection attempts	Supported
`.reconnectWait(Int)`	Min seconds before reconnect	Supported
`.reconnectWaitMax(Int)`	Max seconds before reconnect	Supported
`.randomizationFactor(Double)`	Reconnect jitter	Supported
`.secure(Bool)`	Secure transports	Supported
`.selfSigned(Bool)`	Self-signed certs (dev only)	Ignored
`.auth([String: Any])`	Authentication payload	Ignored

Building

This project is a Swift Package Manager module that uses the Skip plugin to build the package for both iOS and Android.

Testing

The module can be tested using the standard swift test command or by running the test target for the macOS destination in Xcode, which will run the Swift tests as well as the transpiled Kotlin JUnit tests in the Robolectric Android simulation environment.

Parity testing can be performed with skip test, which will output a table of the test results for both platforms.