Swift中使用NetService无法获取网络服务地址与端口的问题

当NetServiceBrowser通过didFind service回调返回服务时，这个服务尚未被解析，此时hostName、port、addresses都是未初始化的状态，所以会出现port=-1、addresses为空数组的情况。必须主动触发服务解析，才能拿到完整的网络信息。

具体修改方案 #

• 新增数组存储找到的NetService实例，避免对象被提前释放
• 在找到服务后，调用resolve(withTimeout:)方法触发解析
• 实现NetServiceDelegate的解析完成回调方法，在回调中获取完整的服务信息
• 可选：处理解析失败的情况

修改后的完整代码 #

import Foundation
import Network

class SocketIoManager: NSObject, NetServiceBrowserDelegate, NetServiceDelegate {
   
    private var browser: NetServiceBrowser!
    // 存储找到的服务，避免被提前释放
    private var discoveredServices = [NetService]()

    private override init() {
        super.init()
        browser = NetServiceBrowser()
        browser.delegate = self
        browser.searchForServices(ofType: "_itworks._tcp", inDomain: "")
    }
    
    // MARK: - NetServiceBrowserDelegate
    func netServiceBrowser(_ browser: NetServiceBrowser, didFind service: NetService, moreComing: Bool) {
        // 保存服务实例
        discoveredServices.append(service)
        // 设置代理并触发解析，超时时间可根据需求调整
        service.delegate = self
        service.resolve(withTimeout: 5.0)
    }
    
    func netServiceBrowser(_ browser: NetServiceBrowser, didRemove service: NetService, moreComing: Bool) {
        // 移除已消失的服务，可选
        if let index = discoveredServices.firstIndex(of: service) {
            discoveredServices.remove(at: index)
        }
    }
    
    // MARK: - NetServiceDelegate
    func netServiceDidResolveAddress(_ service: NetService) {
        // 解析完成，此时可以获取完整的服务信息
        let serviceInfo = serializeService(toDictionary: service)
        print("解析完成的服务信息：\(serviceInfo)")
        
        // 可选：解析完成后停止监听该服务，清理内存
        service.stop()
        if let index = discoveredServices.firstIndex(of: service) {
            discoveredServices.remove(at: index)
        }
    }
    
    func netService(_ service: NetService, didNotResolve errorDict: [String : NSNumber]) {
        // 处理解析失败的情况
        print("服务解析失败：\(errorDict)")
        if let index = discoveredServices.firstIndex(of: service) {
            discoveredServices.remove(at: index)
        }
    }
    
    // MARK: - 工具方法
    private func serializeService(toDictionary service: NetService) -> [String: Any] {
        var serviceInfo: [String: Any] = [:]
        serviceInfo["name"] = service.name
        serviceInfo["host"] = service.hostName
        serviceInfo["port"] = service.port
        serviceInfo["addresses"] = addressesFromService(service)
        return serviceInfo
    }
    
    func addressesFromService(_ service: NetService) -> [String] {
        var addresses = [String]()
        guard let serviceAddresses = service.addresses else { return addresses }

        var addressBuffer = [CChar](repeating: 0, count: Int(INET6_ADDRSTRLEN))

        for data in serviceAddresses {
            memset(&addressBuffer, 0, Int(INET6_ADDRSTRLEN))

            typealias IPSocketAddress = (
                sa: sockaddr,
                ipv4: sockaddr_in,
                ipv6: sockaddr_in6
            )

            let socketAddress = data.withUnsafeBytes { pointer -> IPSocketAddress in
                return pointer.baseAddress!.assumingMemoryBound(to: IPSocketAddress.self).pointee
            }

            if socketAddress.sa.sa_family == sa_family_t(AF_INET) || socketAddress.sa.sa_family == sa_family_t(AF_INET6) {
                let addressStr = socketAddress.sa.sa_family == sa_family_t(AF_INET)
                    ? inet_ntop(AF_INET, &socketAddress.ipv4.sin_addr, &addressBuffer, socklen_t(INET6_ADDRSTRLEN))
                    : inet_ntop(AF_INET6, &socketAddress.ipv6.sin6_addr, &addressBuffer, socklen_t(INET6_ADDRSTRLEN))

                if let addressStr = addressStr, let address = String(utf8String: addressStr) {
                    addresses.append(address)
                }
            }
        }

        return addresses
    }
}

关键说明 #

• 必须持有NetService实例：如果不将服务存入discoveredServices数组，服务对象可能会被ARC提前释放，导致解析回调无法触发。
• 解析超时设置：resolve(withTimeout:)的超时时间可以根据网络环境调整，单位是秒。
• 解析完成后的清理：解析完成或失败后，建议从数组中移除对应的服务，并调用service.stop()停止监听，避免内存泄漏。

内容的提问来源于stack exchange，提问作者Pastor J.G Seigle