/swift-networking

Migration Guide

API Mapping

From BSD Sockets

// WRONG - Blocks main thread
int sock = socket(AF_INET, SOCK_STREAM, 0);
connect(sock, &addr, addrlen);  // BLOCKS

// CORRECT
let connection = NWConnection(host: "example.com", port: 443, using: .tls)
connection.stateUpdateHandler = { [weak self] state in
    if case .ready = state { self?.sendData() }
}
connection.start(queue: .main)  // Non-blocking

From SCNetworkReachability

// WRONG - Race condition
if SCNetworkReachabilityGetFlags(reachability, &flags) {
    if flags.contains(.reachable) {
        connection.start()  // Network may change!
    }
}

// CORRECT - Use waiting state
connection.stateUpdateHandler = { state in
    switch state {
    case .waiting: showStatus("Waiting for network...")
    case .ready: startCommunication()
    case .failed: showError("Failed")
    default: break
    }
}

From getaddrinfo

// WRONG - Misses Happy Eyeballs, proxies
getaddrinfo("example.com", "443", &hints, &results);

// CORRECT - Framework handles DNS, IPv4/IPv6 racing
let connection = NWConnection(
    host: NWEndpoint.Host("example.com"),  // Hostname, not IP
    port: 443, using: .tls
)

From URLSession StreamTask

// Before
let task = URLSession.shared.streamTask(withHostName: "example.com", port: 443)
task.write(data, timeout: 10) { _ in }

// After (iOS 26+)
let connection = NetworkConnection(to: .hostPort(host: "example.com", port: 443)) { TLS() }
try await connection.send(data)

From NWConnection to NetworkConnection

// Before
connection.stateUpdateHandler = { [weak self] state in
    if case .ready = state { self?.sendData() }
}

// After
Task {
    for await state in connection.states {
        if case .ready = state {
            try await connection.send(data)
        }
    }
}

Migration Checklist

• Removed SCNetworkReachability
• Removed getaddrinfo / manual DNS
• Removed CFSocket / NSStream
• Using hostnames, not IPs
• Handling .waiting state
• Using [weak self] in NWConnection handlers
• Tested on real device
• Tested WiFi/cellular transitions