add a ping service (#372)

* add a ping service

* add examples and public api file

* add minecraft server ping

minecraft/handler/minecraft.go

@@ -0,0 +1,42 @@
+package handler
+
+import (
+	"context"
+
+	"github.com/iverly/go-mcping/mcping"
+	"github.com/micro/micro/v3/service/errors"
+	pb "github.com/micro/services/minecraft/proto"
+)
+
+type Minecraft struct{}
+
+func (m *Minecraft) Ping(ctx context.Context, req *pb.PingRequest, rsp *pb.PingResponse) error {
+	if len(req.Address) == 0 {
+		return errors.BadRequest("minecraft.ping", "missing address")
+	}
+
+	pinger := mcping.NewPinger()
+	resp, err := pinger.Ping(req.Address, 25565)
+	if err != nil {
+		return err
+	}
+
+	var samples []*pb.PlayerSample
+	for _, sample := range resp.Sample {
+		samples = append(samples, &pb.PlayerSample{
+			Uuid: sample.UUID,
+			Name: sample.Name,
+		})
+	}
+
+	rsp.Latency = uint32(resp.Latency)
+	rsp.Players = int32(resp.PlayerCount.Online)
+	rsp.MaxPlayers = int32(resp.PlayerCount.Max)
+	rsp.Protocol = int32(resp.Protocol)
+	rsp.Favicon = resp.Favicon
+	rsp.Motd = resp.Motd
+	rsp.Version = resp.Version
+	rsp.Sample = samples
+
+	return nil
+}