问题

承接上文[iOS实现WIFI传书]，如果去掉局域网会如何？能否实现设备间文件传输

iOS设备间的数据传输常用方式：

  1.蓝牙
  2.airdrop
  3.MultipeerConnectivity

该篇单讲MultipeerConnectivity

上菜

设备作为服务端

• 要有一个标志自己的PeerID

lazy var me: MCPeerID = {
    let peer = MCPeerID(displayName: UIDevice.current.name)
    return peer
}()

• 一个session

lazy var session: MCSession = {
    let ss = MCSession(peer: me, securityIdentity: nil, encryptionPreference: .none)
    ss.delegate = self
    return ss
}()

• 广播出去，其他设备才能搜索到

lazy var advertiser: MCNearbyServiceAdvertiser = {
    let advertiser = MCNearbyServiceAdvertiser(peer: me, discoveryInfo: ["demo": "data"], serviceType: "shanzhai")
    advertiser.delegate = self
    return advertiser
}()

• 开始广播

advertiser.startAdvertisingPeer()

• 广播的代理方法执行

extension MultipeerConnectVC: MCNearbyServiceAdvertiserDelegate {
    func advertiser(_ advertiser: MCNearbyServiceAdvertiser, didReceiveInvitationFromPeer peerID: MCPeerID, withContext context: Data?, invitationHandler: @escaping (Bool, MCSession?) -> Void) {
        // 确认连接，赋值session
        invitationHandler(true, session)
    }
    
    func advertiser(_ advertiser: MCNearbyServiceAdvertiser, didNotStartAdvertisingPeer error: Error) {
        advertiser.stopAdvertisingPeer()
        print("Woops! Advertising failed with error \(String(describing: error))")
    }
}

设备作为客户端

• 要有一个标志自己的PeerID

lazy var me: MCPeerID = {
    let peer = MCPeerID(displayName: UIDevice.current.name)
    return peer
}()

• 一个session

lazy var session: MCSession = {
    let ss = MCSession(peer: me, securityIdentity: nil, encryptionPreference: .none)
    ss.delegate = self
    return ss
}()

• 需要一个搜索PeerID

lazy var browser: MCNearbyServiceBrowser = {
    let bs = MCNearbyServiceBrowser(peer: me, serviceType: "shanzhai")
    bs.delegate = self
    return bs
}()

• 开始搜索

browser.startBrowsingForPeers()

• 代理中检索到附近的PeerID, 检索到可以自己存下来，也可以直接链接，依业务需求来，此处直连

extension MultipeerConnectVC: MCNearbyServiceBrowserDelegate {
    func browser(_ browser: MCNearbyServiceBrowser, foundPeer peerID: MCPeerID, withDiscoveryInfo info: [String : String]?) {
        print("search peerId = \(peerID)")
        //搜到了peerID可以放入数组中，选择想要连接的peerID连接，这里直接连接
        browser.invitePeer(peerID, to: session, withContext: nil, timeout: 10)
    }
    
    func browser(_ browser: MCNearbyServiceBrowser, lostPeer peerID: MCPeerID) {
        print("lost peerID = \(peerID)")
    }
    
    func browser(_ browser: MCNearbyServiceBrowser, didNotStartBrowsingForPeers error: Error) {
        print("error = \(error)")
    }
}

连接过程看Session，session代理中看各个过程

extension MultipeerConnectVC: MCSessionDelegate {

    func session(_ session: MCSession, peer peerID: MCPeerID, didChange state: MCSessionState) {
    }
    
    func session(_ session: MCSession, didReceive data: Data, fromPeer peerID: MCPeerID) {
        
    }
    
    func session(_ session: MCSession, didReceive stream: InputStream, withName streamName: String, fromPeer peerID: MCPeerID) {
        
    }
    
    func session(_ session: MCSession, didStartReceivingResourceWithName resourceName: String, fromPeer peerID: MCPeerID, with progress: Progress) {
    }
    
    func session(_ session: MCSession, didFinishReceivingResourceWithName resourceName: String, fromPeer peerID: MCPeerID, at localURL: URL?, withError error: Error?) { 

    }
}

• 代理方法didChange didChange方法中 MCSessionState == .connected，表示连接上，连接上后可传递数据

• 代理方法didFinishReceivingResourceWithName，可以查看接收到的数据

• 也可使用MCBrowserViewController，搜索到的PeerID，无需自己写界面

结语

该方式并未打通iOS与Android，适用于苹果设备之间的无网络数据传输。FileChat在苹果设备之间的实现方式应该是基于此进行的