Rork Max 生成アプリで端末同士を直接つなぐ — MultipeerConnectivity が無言で失敗する Local Network 権限の罠

<!-- Info.plist -->
<key>NSLocalNetworkUsageDescription</key>
<string>近くの端末とプリセットを直接共有するために、ローカルネットワーク上の端末を探します。</string>
<key>NSBonjourServices</key>
<array>
  <string>_dolicoshare._tcp</string>
  <string>_dolicoshare._udp</string>
</array>

import os
 
let shareLog = Logger(subsystem: "net.rorklab.share", category: "multipeer")
// 使い方: shareLog.info("browser: found peer \(peerID.displayName, privacy: .public)")

import MultipeerConnectivity
import os
 
@MainActor
final class NearbyShareManager: NSObject, ObservableObject {
    // serviceType は 1〜15 文字・英小文字/数字/ハイフンのみ（後述の罠を参照）
    private let serviceType = "dolicoshare"
    private let myPeerID = MCPeerID(displayName: UUID().uuidString.prefix(8).description)
 
    private lazy var session: MCSession = {
        let s = MCSession(peer: myPeerID, securityIdentity: nil,
                          encryptionPreference: .required)
        s.delegate = self
        return s
    }()
 
    private lazy var advertiser = MCNearbyServiceAdvertiser(
        peer: myPeerID, discoveryInfo: nil, serviceType: serviceType)
    private lazy var browser = MCNearbyServiceBrowser(
        peer: myPeerID, serviceType: serviceType)
 
    private let log = Logger(subsystem: "net.rorklab.share", category: "multipeer")
 
    @Published private(set) var foundPeers: [MCPeerID] = []
    @Published private(set) var connectedPeers: [MCPeerID] = []
 
    func start() {
        advertiser.delegate = self
        browser.delegate = self
        advertiser.startAdvertisingPeer()
        browser.startBrowsingForPeers()
        log.info("start advertising and browsing")
    }
 
    func stop() {
        advertiser.stopAdvertisingPeer()
        browser.stopBrowsingForPeers()
        session.disconnect()
        foundPeers.removeAll()
        connectedPeers.removeAll()
    }
 
    func invite(_ peerID: MCPeerID) {
        // 相手を自分のセッションへ招待。timeout は短すぎると取りこぼす
        browser.invitePeer(peerID, to: session, withContext: nil, timeout: 20)
    }
 
    func send(_ data: Data) {
        guard !session.connectedPeers.isEmpty else { return }
        do {
            try session.send(data, toPeers: session.connectedPeers, with: .reliable)
        } catch {
            log.error("send failed: \(error.localizedDescription, privacy: .public)")
        }
    }
}

extension NearbyShareManager: MCNearbyServiceBrowserDelegate {
    nonisolated func browser(_ browser: MCNearbyServiceBrowser,
                             foundPeer peerID: MCPeerID,
                             withDiscoveryInfo info: [String: String]?) {
        Task { @MainActor in
            if !foundPeers.contains(peerID) { foundPeers.append(peerID) }
            log.info("found peer \(peerID.displayName, privacy: .public)")
        }
    }
    nonisolated func browser(_ browser: MCNearbyServiceBrowser,
                             lostPeer peerID: MCPeerID) {
        Task { @MainActor in foundPeers.removeAll { $0 == peerID } }
    }
}
 
extension NearbyShareManager: MCNearbyServiceAdvertiserDelegate {
    nonisolated func advertiser(_ advertiser: MCNearbyServiceAdvertiser,
                                didReceiveInvitationFromPeer peerID: MCPeerID,
                                withContext context: Data?,
                                invitationHandler: @escaping (Bool, MCSession?) -> Void) {
        // ここで確認ダイアログを挟むのが本来は望ましい。最小構成では自動受理
        Task { @MainActor in invitationHandler(true, session) }
    }
}
 
extension NearbyShareManager: MCSessionDelegate {
    nonisolated func session(_ session: MCSession, peer peerID: MCPeerID,
                             didChange state: MCSessionState) {
        Task { @MainActor in
            switch state {
            case .connected:
                if !connectedPeers.contains(peerID) { connectedPeers.append(peerID) }
            case .notConnected:
                connectedPeers.removeAll { $0 == peerID }
            case .connecting:
                break
            @unknown default:
                break
            }
        }
    }
    nonisolated func session(_ session: MCSession, didReceive data: Data,
                             fromPeer peerID: MCPeerID) {
        // 受信データの処理（画像 Data のデコード等）
    }
    nonisolated func session(_ s: MCSession, didReceive stream: InputStream,
                             withName n: String, fromPeer p: MCPeerID) {}
    nonisolated func session(_ s: MCSession, didStartReceivingResourceWithName n: String,
                             fromPeer p: MCPeerID, with progress: Progress) {}
    nonisolated func session(_ s: MCSession, didFinishReceivingResourceWithName n: String,
                             fromPeer p: MCPeerID, at localURL: URL?,
                             withError error: Error?) {}
}

struct NearbyShareView: View {
    @StateObject private var share = NearbyShareManager()
 
    var body: some View {
        List {
            Section("接続中") {
                ForEach(share.connectedPeers, id: \.self) { Text($0.displayName) }
            }
            Section("近くの端末") {
                ForEach(share.foundPeers, id: \.self) { peer in
                    Button(peer.displayName) { share.invite(peer) }
                }
            }
        }
        .onAppear { share.start() }
        .onDisappear { share.stop() }
    }
}