diff --git a/README.md b/README.md
index 310a1f3d..e7b6fc9f 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,6 @@ this is ion golang sdk for ion-sfu
 
 - [x] Subscribe from session
 - [x] Publish webm to session
+- [x] Save stream to file
 - [ ] Publish media device to session
-- [ ] Save stream to file
 - [ ] Support ion cluster
diff --git a/client.go b/client.go
index f3dbf29f..c74c595c 100644
--- a/client.go
+++ b/client.go
@@ -26,6 +26,7 @@ type Call struct {
 
 // Client a sdk client
 type Client struct {
+	ID     string
 	pub    *Transport
 	sub    *Transport
 	cfg    WebRTCTransportConfig
@@ -49,8 +50,9 @@ type Client struct {
 }
 
 // NewClient create a sdk client
-func NewClient(addr string, cfg WebRTCTransportConfig) *Client {
+func NewClient(addr, id string, cfg WebRTCTransportConfig) *Client {
 	c := &Client{
+		ID:             id,
 		signal:         NewSignal(addr),
 		cfg:            cfg,
 		notify:         make(chan struct{}),
@@ -178,7 +180,7 @@ func (c *Client) Join(sid string) error {
 	if err != nil {
 		return err
 	}
-	err = c.signal.Join(sid, offer)
+	err = c.signal.Join(sid, c.ID, offer)
 	return err
 }
 
diff --git a/engine.go b/engine.go
index 22109ce6..a4019f14 100644
--- a/engine.go
+++ b/engine.go
@@ -44,7 +44,7 @@ func (e *Engine) AddClient(addr, sid, cid string) *Client {
 	if e.clients[sid] == nil {
 		e.clients[sid] = make(map[string]*Client)
 	}
-	c := NewClient(addr, e.cfg.WebRTC)
+	c := NewClient(addr, cid, e.cfg.WebRTC)
 	e.clients[sid][cid] = c
 	e.Unlock()
 	if c == nil {
diff --git a/example/simple/README.md b/example/simple/README.md
new file mode 100644
index 00000000..465a6be1
--- /dev/null
+++ b/example/simple/README.md
@@ -0,0 +1,26 @@
+# Simple
+
+This is a simple example to show:
+
+* Publishs webm to session
+* Subscribe from session and save to disk
+
+## Quick Start
+
+### 1 build
+
+```
+go build main.go
+```
+
+### 2 use
+
+```
+# see ./main --help
+./main -file /Volumes/vm/media/djrm480p.webm  -addr "localhost:8000" -session 'test room'
+```
+
+### 3 tips
+
+* people in the same room will see your movie
+* you will find ogg and ivf on your disk if others publish streams in the same room
diff --git a/example/simple/main.go b/example/simple/main.go
new file mode 100644
index 00000000..31ff8274
--- /dev/null
+++ b/example/simple/main.go
@@ -0,0 +1,98 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"strings"
+
+	log "github.com/pion/ion-log"
+	sdk "github.com/pion/ion-sdk-go"
+	"github.com/pion/webrtc/v3"
+	"github.com/pion/webrtc/v3/pkg/media"
+	"github.com/pion/webrtc/v3/pkg/media/ivfwriter"
+	"github.com/pion/webrtc/v3/pkg/media/oggwriter"
+)
+
+func saveToDisk(track *webrtc.TrackRemote, receiver *webrtc.RTPReceiver) {
+	codec := track.Codec()
+	var fileWriter media.Writer
+	var err error
+	if strings.EqualFold(codec.MimeType, webrtc.MimeTypeOpus) {
+		log.Infof("Got Opus track, saving to disk as ogg (48 kHz, 2 channels)")
+		fileWriter, err = oggwriter.New(fmt.Sprintf("%d_%d.ogg", codec.PayloadType, track.SSRC()), 48000, 2)
+	} else if strings.EqualFold(codec.MimeType, webrtc.MimeTypeVP8) {
+		log.Infof("Got VP8 track, saving to disk as ivf")
+		fileWriter, err = ivfwriter.New(fmt.Sprintf("%d_%d.ivf", codec.PayloadType, track.SSRC()))
+	}
+
+	if err != nil {
+		log.Errorf("err=%v", err)
+		fileWriter.Close()
+		return
+	}
+
+	for {
+		rtpPacket, _, err := track.ReadRTP()
+		if err != nil {
+			panic(err)
+		}
+		if err := fileWriter.WriteRTP(rtpPacket); err != nil {
+			panic(err)
+		}
+	}
+}
+
+func main() {
+	// init log
+	fixByFile := []string{"asm_amd64.s", "proc.go", "icegatherer.go"}
+	fixByFunc := []string{"AddProducer", "NewClient"}
+	log.Init("debug", fixByFile, fixByFunc)
+
+	// parse flag
+	var session, addr, file string
+	flag.StringVar(&file, "file", "./file.webm", "Path to the file media")
+	flag.StringVar(&addr, "addr", "localhost:50051", "Ion-sfu grpc addr")
+	flag.StringVar(&session, "session", "test room", "join session name")
+	flag.Parse()
+
+	// add stun servers
+	webrtcCfg := webrtc.Configuration{
+		ICEServers: []webrtc.ICEServer{
+			webrtc.ICEServer{
+				URLs: []string{"stun:stun.stunprotocol.org:3478", "stun:stun.l.google.com:19302"},
+			},
+		},
+	}
+
+	config := sdk.Config{
+		Log: log.Config{
+			Level: "debug",
+		},
+		WebRTC: sdk.WebRTCTransportConfig{
+			Configuration: webrtcCfg,
+		},
+	}
+	// new sdk engine
+	e := sdk.NewEngine(addr, config)
+
+	// get a client from engine
+	c := e.AddClient(addr, session, "client id")
+
+	// subscribe rtp from sessoin
+	// comment this if you don't need save to file
+	c.OnTrack = saveToDisk
+
+	// client join a session
+	err := c.Join(session)
+
+	// publish file to session if needed
+	if err == nil && file != "" {
+		err = c.PublishWebm(file)
+		if err != nil {
+			log.Errorf("err=%v", err)
+		}
+	} else {
+		log.Errorf("err=%v", err)
+	}
+	select {}
+}
diff --git a/go.mod b/go.mod
index c2e9717c..4df64b2a 100644
--- a/go.mod
+++ b/go.mod
@@ -6,9 +6,9 @@ require (
 	github.com/ebml-go/ebml v0.0.0-20160925193348-ca8851a10894 // indirect
 	github.com/ebml-go/webm v0.0.0-20160924163542-629e38feef2a
 	github.com/petar/GoLLRB v0.0.0-20190514000832-33fb24c13b99 // indirect
-	github.com/pion/ice/v2 v2.0.14
+	github.com/pion/ice/v2 v2.0.15
 	github.com/pion/ion-log v1.0.0
-	github.com/pion/ion-sfu v1.7.8
+	github.com/pion/ion-sfu v1.9.1-0.20210212123851-331f8471352c
 	github.com/pion/webrtc/v3 v3.0.4
 	google.golang.org/grpc v1.35.0
 )
diff --git a/go.sum b/go.sum
index c5316fa5..c6a96d45 100644
--- a/go.sum
+++ b/go.sum
@@ -138,6 +138,8 @@ github.com/google/renameio v0.1.0/go.mod h1:KWCgfxg9yswjAJkECMjeO8J8rahYeXnNhOm4
 github.com/google/uuid v1.0.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/google/uuid v1.1.2 h1:EVhdT+1Kseyi1/pUmXKaFxYsDNy9RQYkMWRH68J/W7Y=
 github.com/google/uuid v1.1.2/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/google/uuid v1.1.5 h1:kxhtnfFVi+rYdOALN0B3k9UT86zVJKfBimRaciULW4I=
+github.com/google/uuid v1.1.5/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/googleapis/gax-go/v2 v2.0.4/go.mod h1:0Wqv26UfaUD9n4G6kQubkQ+KchISgw+vpHVxEJEs9eg=
 github.com/googleapis/gax-go/v2 v2.0.5/go.mod h1:DWXyrwAJ9X0FpwwEdw+IPEYBICEFu5mhpdKc/us6bOk=
 github.com/gopherjs/gopherjs v0.0.0-20181017120253-0766667cb4d1/go.mod h1:wJfORRmW1u3UXTncJ5qlYoELFm8eSnnEO6hX4iZ3EWY=
@@ -267,12 +269,16 @@ github.com/pion/dtls/v2 v2.0.4 h1:WuUcqi6oYMu/noNTz92QrF1DaFj4eXbhQ6dzaaAwOiI=
 github.com/pion/dtls/v2 v2.0.4/go.mod h1:qAkFscX0ZHoI1E07RfYPoRw3manThveu+mlTDdOxoGI=
 github.com/pion/ice/v2 v2.0.14 h1:FxXxauyykf89SWAtkQCfnHkno6G8+bhRkNguSh9zU+4=
 github.com/pion/ice/v2 v2.0.14/go.mod h1:wqaUbOq5ObDNU5ox1hRsEst0rWfsKuH1zXjQFEWiZwM=
+github.com/pion/ice/v2 v2.0.15 h1:KZrwa2ciL9od8+TUVJiYTNsCW9J5lktBjGwW1MacEnQ=
+github.com/pion/ice/v2 v2.0.15/go.mod h1:ZIiVGevpgAxF/cXiIVmuIUtCb3Xs4gCzCbXB6+nFkSI=
 github.com/pion/interceptor v0.0.9 h1:fk5hTdyLO3KURQsf/+RjMpEm4NE3yeTY9Kh97b5BvwA=
 github.com/pion/interceptor v0.0.9/go.mod h1:dHgEP5dtxOTf21MObuBAjJeAayPxLUAZjerGH8Xr07c=
 github.com/pion/ion-log v1.0.0 h1:2lJLImCmfCWCR38hLWsjQfBWe6NFz/htbqiYHwvOP/Q=
 github.com/pion/ion-log v1.0.0/go.mod h1:jwcla9KoB9bB/4FxYDSRJPcPYSLp5XiUUMnOLaqwl4E=
 github.com/pion/ion-sfu v1.7.8 h1:5DBi3m1eZVOQBcJiV7GPOWLHY56LpDhIBRa8ZmMhz/k=
 github.com/pion/ion-sfu v1.7.8/go.mod h1:3VcBm7RSsSzB09HH4g5ka63pVvx7UHI4vL2XNFt1jA8=
+github.com/pion/ion-sfu v1.9.1-0.20210212123851-331f8471352c h1:+tg7My3x1JEKhDWNo+o3aza7bBlkKI2v3LdhZnIrCeA=
+github.com/pion/ion-sfu v1.9.1-0.20210212123851-331f8471352c/go.mod h1:MKDh4JSLpBA/hFeYAYALb6nYpe6Ruknd3pmxPMbdpM8=
 github.com/pion/logging v0.2.2 h1:M9+AIj/+pxNsDfAT64+MAVgJO0rsyLnoJKCqf//DoeY=
 github.com/pion/logging v0.2.2/go.mod h1:k0/tDVsRCX2Mb2ZEmTqNa7CWsQPc+YYCB7Q+5pahoms=
 github.com/pion/mdns v0.0.4 h1:O4vvVqr4DGX63vzmO6Fw9vpy3lfztVWHGCQfyw0ZLSY=
@@ -297,6 +303,7 @@ github.com/pion/transport v0.8.10/go.mod h1:tBmha/UCjpum5hqTWhfAEs3CO4/tHSg0MYRh
 github.com/pion/transport v0.10.0/go.mod h1:BnHnUipd0rZQyTVB2SBGojFHT9CBt5C5TcsJSQGkvSE=
 github.com/pion/transport v0.10.1/go.mod h1:PBis1stIILMiis0PewDw91WJeLJkyIMcEk+DwKOzf4A=
 github.com/pion/transport v0.12.0/go.mod h1:N3+vZQD9HlDP5GWkZ85LohxNsDcNgofQmyL6ojX5d8Q=
+github.com/pion/transport v0.12.1/go.mod h1:N3+vZQD9HlDP5GWkZ85LohxNsDcNgofQmyL6ojX5d8Q=
 github.com/pion/transport v0.12.2 h1:WYEjhloRHt1R86LhUKjC5y+P52Y11/QqEUalvtzVoys=
 github.com/pion/transport v0.12.2/go.mod h1:N3+vZQD9HlDP5GWkZ85LohxNsDcNgofQmyL6ojX5d8Q=
 github.com/pion/turn/v2 v2.0.5 h1:iwMHqDfPEDEOFzwWKT56eFmh6DYC6o/+xnLAEzgISbA=
diff --git a/signal.go b/signal.go
index b55551b3..4dd304d8 100644
--- a/signal.go
+++ b/signal.go
@@ -133,8 +133,8 @@ func (s *Signal) onSignalHandle() error {
 	}
 }
 
-func (s *Signal) Join(sid string, offer webrtc.SessionDescription) error {
-	log.Infof("[Signal.Join] sid=%v offer=%v", sid, offer)
+func (s *Signal) Join(sid, uid string, offer webrtc.SessionDescription) error {
+	log.Infof("[Signal.Join] sid=%v uid=%v, offer=%v", sid, uid, offer)
 	marshalled, err := json.Marshal(offer)
 	if err != nil {
 		return err
@@ -146,6 +146,7 @@ func (s *Signal) Join(sid string, offer webrtc.SessionDescription) error {
 			Payload: &pb.SignalRequest_Join{
 				Join: &pb.JoinRequest{
 					Sid:         sid,
+					Uid:         uid,
 					Description: marshalled,
 				},
 			},