Provide easier access to evcc web interface (evcc-io#2492)

- Use mdns to provide access to the evcc website via `http://evcc.local:7070`
- Correctly shutdown the mdns announcement on exit
- Unknown: We need to check how this works in a docker environment, as that may provide unreachable IP addresses

cmd/root.go

@@ -2,10 +2,12 @@ package cmd
 
 import (
 	"fmt"
+	"net"
 	"net/http"
 	_ "net/http/pprof" // pprof handler
 	"os"
 	"os/signal"
+	"strconv"
 	"sync"
 	"syscall"
 	"time"
@@ -16,6 +18,7 @@ import (
 	"github.com/evcc-io/evcc/util"
 	"github.com/evcc-io/evcc/util/pipe"
 	"github.com/evcc-io/evcc/util/sponsor"
+	"github.com/grandcat/zeroconf"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 
 	"github.com/spf13/cobra"
@@ -190,6 +193,17 @@ func run(cmd *cobra.Command, args []string) {
 	socketHub := server.NewSocketHub()
 	httpd := server.NewHTTPd(uri, site, socketHub, cache)
 
+	// announce webserver on mDNS
+	if _, port, err := net.SplitHostPort(uri); err == nil {
+		if portInt, err := strconv.Atoi(port); err == nil {
+			if zc, err := zeroconf.RegisterProxy("evcc Website", "_http._tcp", "local.", portInt, "evcc", nil, []string{}, nil); err == nil {
+				shutdown.Register(zc.Shutdown)
+			} else {
+				log.ERROR.Printf("mDNS announcement: %s", err)
+			}
+		}
+	}
+
 	// metrics
 	if viper.GetBool("metrics") {
 		httpd.Router().Handle("/metrics", promhttp.Handler())