func checkServer(deviceID protocol.DeviceID, server string) checkResult {
	disco, err := discover.NewGlobal(server, tls.Certificate{}, nil)
	if err != nil {
		return checkResult{error: err}
	}

	res := make(chan checkResult, 1)

	time.AfterFunc(timeout, func() {
		res <- checkResult{error: errors.New("timeout")}
	})

	go func() {
		addresses, err := disco.Lookup(deviceID)
		res <- checkResult{addresses: addresses, error: err}
	}()

	return <-res
}

//.........这里部分代码省略.........
	// The externalAddr tracks our external addresses for discovery purposes.

	var addrList *addressLister

	// Start UPnP

	if opts.UPnPEnabled {
		upnpSvc := newUPnPSvc(cfg, addr.Port)
		mainSvc.Add(upnpSvc)

		// The external address tracker needs to know about the UPnP service
		// so it can check for an external mapped port.
		addrList = newAddressLister(upnpSvc, cfg)
	} else {
		addrList = newAddressLister(nil, cfg)
	}

	// Start relay management

	var relaySvc *relay.Svc
	if opts.RelaysEnabled && (opts.GlobalAnnEnabled || opts.RelayWithoutGlobalAnn) {
		relaySvc = relay.NewSvc(cfg, tlsCfg)
		mainSvc.Add(relaySvc)
	}

	// Start discovery

	cachedDiscovery := discover.NewCachingMux()
	mainSvc.Add(cachedDiscovery)

	if cfg.Options().GlobalAnnEnabled {
		for _, srv := range cfg.GlobalDiscoveryServers() {
			l.Infoln("Using discovery server", srv)
			gd, err := discover.NewGlobal(srv, cert, addrList, relaySvc)
			if err != nil {
				l.Warnln("Global discovery:", err)
				continue
			}

			// Each global discovery server gets its results cached for five
			// minutes, and is not asked again for a minute when it's returned
			// unsuccessfully.
			cachedDiscovery.Add(gd, 5*time.Minute, time.Minute, globalDiscoveryPriority)
		}
	}

	if cfg.Options().LocalAnnEnabled {
		// v4 broadcasts
		bcd, err := discover.NewLocal(myID, fmt.Sprintf(":%d", cfg.Options().LocalAnnPort), addrList, relaySvc)
		if err != nil {
			l.Warnln("IPv4 local discovery:", err)
		} else {
			cachedDiscovery.Add(bcd, 0, 0, ipv4LocalDiscoveryPriority)
		}
		// v6 multicasts
		mcd, err := discover.NewLocal(myID, cfg.Options().LocalAnnMCAddr, addrList, relaySvc)
		if err != nil {
			l.Warnln("IPv6 local discovery:", err)
		} else {
			cachedDiscovery.Add(mcd, 0, 0, ipv6LocalDiscoveryPriority)
		}
	}

	// GUI

	setupGUI(mainSvc, cfg, m, apiSub, cachedDiscovery, relaySvc, errors, systemLog)

func main() {
	flag.BoolVar(&showVersion, "version", false, "Show version")

	flag.Usage = usageFor(flag.CommandLine, usage, fmt.Sprintf(extraUsage, baseDirs["config"]))
	flag.Parse()

	if showVersion {
		fmt.Println(Version)
		return
	}

	if err := expandLocations(); err != nil {
		l.Fatalln(err)
	}

	// Ensure that our home directory exists.
	ensureDir(baseDirs["config"], 0700)

	// Ensure that that we have a certificate and key.
	tlsCfg, cert := getTlsConfig()

	// We reinitialize the predictable RNG with our device ID, to get a
	// sequence that is always the same but unique to this syncthing instance.
	predictableRandom.Seed(seedFromBytes(cert.Certificate[0]))

	myID = protocol.NewDeviceID(cert.Certificate[0])
	l.SetPrefix(fmt.Sprintf("[%s] ", myID.String()[:5]))

	l.Infoln("Started syncthingfuse v.", LongVersion)
	l.Infoln("My ID:", myID)

	cfg := getConfiguration()

	if info, err := os.Stat(cfg.Raw().MountPoint); err == nil {
		if !info.Mode().IsDir() {
			l.Fatalln("Mount point (", cfg.Raw().MountPoint, ") must be a directory, but isn't")
			os.Exit(1)
		}
	} else {
		l.Infoln("Mount point (", cfg.Raw().MountPoint, ") does not exist, creating it")
		err = os.MkdirAll(cfg.Raw().MountPoint, 0700)
		if err != nil {
			l.Warnln("Error creating mount point", cfg.Raw().MountPoint, err)
			l.Warnln("Sometimes, SyncthingFUSE doesn't shut down and unmount cleanly,")
			l.Warnln("If you don't know of any other file systems you have mounted at")
			l.Warnln("the mount point, try running the command below to unmount, then")
			l.Warnln("start SyncthingFUSE again.")
			l.Warnln("    umount", cfg.Raw().MountPoint)
			l.Fatalln("Cannot create missing mount point")
			os.Exit(1)
		}
	}

	mainSvc := suture.New("main", suture.Spec{
		Log: func(line string) {
			l.Debugln(line)
		},
	})
	mainSvc.ServeBackground()

	database := openDatabase(cfg)

	m = model.NewModel(cfg, database)

	lans, _ := osutil.GetLans()

	// Start discovery
	cachedDiscovery := discover.NewCachingMux()
	mainSvc.Add(cachedDiscovery)

	// Start connection management
	connectionsService := connections.NewService(cfg.AsStCfg(myID), myID, m, tlsCfg, cachedDiscovery, bepProtocolName, tlsDefaultCommonName, lans)
	mainSvc.Add(connectionsService)

	if cfg.Raw().Options.GlobalAnnounceEnabled {
		for _, srv := range cfg.Raw().Options.GlobalAnnounceServers {
			l.Infoln("Using discovery server", srv)
			gd, err := discover.NewGlobal(srv, cert, connectionsService)
			if err != nil {
				l.Warnln("Global discovery:", err)
				continue
			}

			// Each global discovery server gets its results cached for five
			// minutes, and is not asked again for a minute when it's returned
			// unsuccessfully.
			cachedDiscovery.Add(gd, 5*time.Minute, time.Minute, globalDiscoveryPriority)
		}
	}

	if cfg.Raw().Options.LocalAnnounceEnabled {
		// v4 broadcasts
		bcd, err := discover.NewLocal(myID, fmt.Sprintf(":%d", cfg.Raw().Options.LocalAnnouncePort), connectionsService)
		if err != nil {
			l.Warnln("IPv4 local discovery:", err)
		} else {
			cachedDiscovery.Add(bcd, 0, 0, ipv4LocalDiscoveryPriority)
		}
		// v6 multicasts
		mcd, err := discover.NewLocal(myID, cfg.Raw().Options.LocalAnnounceMCAddr, connectionsService)
//.........这里部分代码省略.........