diff --git a/.gitignore b/.gitignore
index 42e539f..8959171 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,5 +3,5 @@ build
 .DS_Store
 nohup.out
 build_config.mk
-var
+var*
 _workspace
\ No newline at end of file
diff --git a/cmd/ledis-server/main.go b/cmd/ledis-server/main.go
index e132506..32be6c2 100644
--- a/cmd/ledis-server/main.go
+++ b/cmd/ledis-server/main.go
@@ -15,12 +15,15 @@ import (
 )
 
 var configFile = flag.String("config", "", "ledisdb config file")
+var addr = flag.String("addr", "", "ledisdb listen address")
+var dataDir = flag.String("data_dir", "", "ledisdb base data dir")
 var dbName = flag.String("db_name", "", "select a db to use, it will overwrite the config's db name")
 var usePprof = flag.Bool("pprof", false, "enable pprof")
 var pprofPort = flag.Int("pprof_port", 6060, "pprof http port")
 var slaveof = flag.String("slaveof", "", "make the server a slave of another instance")
 var readonly = flag.Bool("readonly", false, "set readonly mode, salve server is always readonly")
 var rpl = flag.Bool("rpl", false, "enable replication or not, slave server is always enabled")
+var rplSync = flag.Bool("rpl_sync", false, "enable sync replication or not")
 
 func main() {
 	runtime.GOMAXPROCS(runtime.NumCPU())
@@ -42,6 +45,14 @@ func main() {
 		return
 	}
 
+	if len(*addr) > 0 {
+		cfg.Addr = *addr
+	}
+
+	if len(*dataDir) > 0 {
+		cfg.DataDir = *dataDir
+	}
+
 	if len(*dbName) > 0 {
 		cfg.DBName = *dbName
 	}
@@ -53,6 +64,7 @@ func main() {
 	} else {
 		cfg.Readonly = *readonly
 		cfg.UseReplication = *rpl
+		cfg.Replication.Sync = *rplSync
 	}
 
 	var app *server.App
diff --git a/server/app.go b/server/app.go
index aeb71a4..0e03b3f 100644
--- a/server/app.go
+++ b/server/app.go
@@ -32,8 +32,9 @@ type App struct {
 	s *script
 
 	// handle slaves
-	slock  sync.Mutex
-	slaves map[*client]struct{}
+	slock        sync.Mutex
+	slaves       map[string]*client
+	slaveSyncAck chan uint64
 
 	snap *snapshotStore
 }
@@ -60,7 +61,8 @@ func NewApp(cfg *config.Config) (*App, error) {
 
 	app.cfg = cfg
 
-	app.slaves = make(map[*client]struct{})
+	app.slaves = make(map[string]*client)
+	app.slaveSyncAck = make(chan uint64)
 
 	var err error
 
diff --git a/server/client.go b/server/client.go
index ef9de76..ba24821 100644
--- a/server/client.go
+++ b/server/client.go
@@ -64,8 +64,6 @@ type client struct {
 
 	lastLogID uint64
 
-	ack *syncAck
-
 	reqErr chan error
 
 	buf bytes.Buffer
@@ -73,6 +71,8 @@ type client struct {
 	tx *ledis.Tx
 
 	script *ledis.Multi
+
+	slaveListeningAddr string
 }
 
 func newClient(app *App) *client {
diff --git a/server/client_resp.go b/server/client_resp.go
index 078a02c..93edef9 100644
--- a/server/client_resp.go
+++ b/server/client_resp.go
@@ -51,7 +51,10 @@ func (c *respClient) run() {
 			log.Fatal("client run panic %s:%v", buf, e)
 		}
 
+		handleQuit := true
 		if c.conn != nil {
+			//if handle quit command before, conn is nil
+			handleQuit = false
 			c.conn.Close()
 		}
 
@@ -60,7 +63,7 @@ func (c *respClient) run() {
 			c.tx = nil
 		}
 
-		c.app.removeSlave(c.client)
+		c.app.removeSlave(c.client, handleQuit)
 	}()
 
 	for {
@@ -144,6 +147,7 @@ func (c *respClient) handleRequest(reqData [][]byte) {
 		c.resp.writeStatus(OK)
 		c.resp.flush()
 		c.conn.Close()
+		c.conn = nil
 		return
 	}
 
diff --git a/server/cmd_replication.go b/server/cmd_replication.go
index 5526d5c..b401f35 100644
--- a/server/cmd_replication.go
+++ b/server/cmd_replication.go
@@ -1,9 +1,12 @@
 package server
 
 import (
+	"encoding/binary"
 	"fmt"
 	"github.com/siddontang/go/hack"
+	"github.com/siddontang/go/num"
 	"github.com/siddontang/ledisdb/ledis"
+	"net"
 	"strconv"
 	"strings"
 	"time"
@@ -92,6 +95,8 @@ func fullsyncCommand(c *client) error {
 	return nil
 }
 
+var dummyBuf = make([]byte, 8)
+
 func syncCommand(c *client) error {
 	args := c.args
 	if len(args) != 1 {
@@ -107,23 +112,69 @@ func syncCommand(c *client) error {
 
 	c.lastLogID = logId - 1
 
-	if c.ack != nil && logId > c.ack.id {
-		asyncNotifyUint64(c.ack.ch, logId)
-		c.ack = nil
+	stat, err := c.app.ldb.ReplicationStat()
+	if err != nil {
+		return err
+	}
+
+	if c.lastLogID > stat.LastID {
+		return fmt.Errorf("invalid sync logid %d > %d + 1", logId, stat.LastID)
+	} else if c.lastLogID == stat.LastID {
+		c.app.slaveAck(c)
 	}
 
 	c.syncBuf.Reset()
 
+	c.syncBuf.Write(dummyBuf)
+
 	if _, _, err := c.app.ldb.ReadLogsToTimeout(logId, &c.syncBuf, 30); err != nil {
 		return err
 	} else {
 		buf := c.syncBuf.Bytes()
 
+		stat, err = c.app.ldb.ReplicationStat()
+		if err != nil {
+			return err
+		}
+
+		binary.BigEndian.PutUint64(buf, stat.LastID)
+
 		c.resp.writeBulk(buf)
 	}
 
-	c.app.addSlave(c)
+	return nil
+}
 
+//inner command, only for replication
+//REPLCONF <option> <value> <option> <value> ...
+func replconfCommand(c *client) error {
+	args := c.args
+	if len(args)%2 != 0 {
+		return ErrCmdParams
+	}
+
+	//now only support "listening-port"
+	for i := 0; i < len(args); i += 2 {
+		switch strings.ToLower(hack.String(args[i])) {
+		case "listening-port":
+			var host string
+			var err error
+			if _, err = num.ParseUint16(hack.String(args[i+1])); err != nil {
+				return err
+			}
+			if host, _, err = net.SplitHostPort(c.remoteAddr); err != nil {
+				return err
+			} else {
+				c.slaveListeningAddr = net.JoinHostPort(host, hack.String(args[i+1]))
+			}
+
+			c.app.addSlave(c)
+		default:
+			return ErrSyntax
+		}
+	}
+
+	c.resp.writeStatus(OK)
 	return nil
 }
 
@@ -131,4 +182,5 @@ func init() {
 	register("slaveof", slaveofCommand)
 	register("fullsync", fullsyncCommand)
 	register("sync", syncCommand)
+	register("replconf", replconfCommand)
 }
diff --git a/server/info.go b/server/info.go
index 194f2b3..ccdba98 100644
--- a/server/info.go
+++ b/server/info.go
@@ -3,6 +3,7 @@ package server
 import (
 	"bytes"
 	"fmt"
+	"github.com/siddontang/go/sync2"
 	"os"
 	"runtime"
 	"strings"
@@ -25,8 +26,11 @@ type info struct {
 	}
 
 	Replication struct {
-		PubLogNum       int64
-		PubLogTotalTime int64 //milliseconds
+		PubLogNum          sync2.AtomicInt64
+		PubLogAckNum       sync2.AtomicInt64
+		PubLogTotalAckTime sync2.AtomicDuration
+
+		MasterLastLogID sync2.AtomicUint64
 	}
 }
 
@@ -149,18 +153,22 @@ func (i *info) dumpReplication(buf *bytes.Buffer) {
 	buf.WriteString("# Replication\r\n")
 
 	p := []infoPair{}
+	i.app.slock.Lock()
 	slaves := make([]string, 0, len(i.app.slaves))
-	for s, _ := range i.app.slaves {
-		slaves = append(slaves, s.remoteAddr)
+	for _, s := range i.app.slaves {
+		slaves = append(slaves, s.slaveListeningAddr)
 	}
+	i.app.slock.Unlock()
 
-	num := i.Replication.PubLogNum
+	num := i.Replication.PubLogNum.Get()
 	p = append(p, infoPair{"pub_log_num", num})
 
-	if num != 0 {
-		p = append(p, infoPair{"pub_log_per_time", i.Replication.PubLogTotalTime / num})
+	ackNum := i.Replication.PubLogAckNum.Get()
+	totalTime := i.Replication.PubLogTotalAckTime.Get().Nanoseconds() / 1e6
+	if ackNum != 0 {
+		p = append(p, infoPair{"pub_log_ack_per_time", totalTime / ackNum})
 	} else {
-		p = append(p, infoPair{"pub_log_per_time", 0})
+		p = append(p, infoPair{"pub_log_ack_per_time", 0})
 	}
 
 	p = append(p, infoPair{"slaveof", i.app.cfg.SlaveOf})
@@ -179,6 +187,8 @@ func (i *info) dumpReplication(buf *bytes.Buffer) {
 		p = append(p, infoPair{"commit_log_id", 0})
 	}
 
+	p = append(p, infoPair{"master_last_log_id", i.Replication.MasterLastLogID.Get()})
+
 	i.dumpPairs(buf, p...)
 }
 
diff --git a/server/replication.go b/server/replication.go
index 7b37de4..47230b1 100644
--- a/server/replication.go
+++ b/server/replication.go
@@ -14,8 +14,8 @@ import (
 	"os"
 	"path"
 	"strconv"
+	"strings"
 	"sync"
-	"sync/atomic"
 	"time"
 )
 
@@ -49,10 +49,17 @@ func newMaster(app *App) *master {
 	return m
 }
 
+var (
+	quitCmd = []byte("*1\r\n$4\r\nquit\r\n")
+)
+
 func (m *master) Close() {
 	ledis.AsyncNotify(m.quit)
 
 	if m.conn != nil {
+		//for replication, we send quit command to close gracefully
+		m.conn.Write(quitCmd)
+
 		m.conn.Close()
 		m.conn = nil
 	}
@@ -77,6 +84,7 @@ func (m *master) connect() error {
 
 		m.rb = bufio.NewReaderSize(m.conn, 4096)
 	}
+
 	return nil
 }
 
@@ -116,6 +124,11 @@ func (m *master) runReplication(restart bool) {
 			}
 		}
 
+		if err := m.replConf(); err != nil {
+			log.Error("replconf error %s", err.Error())
+			return
+		}
+
 		if restart {
 			if err := m.fullSync(); err != nil {
 				if m.conn != nil {
@@ -148,10 +161,32 @@ func (m *master) runReplication(restart bool) {
 }
 
 var (
-	fullSyncCmd   = []byte("*1\r\n$8\r\nfullsync\r\n")  //fullsync
-	syncCmdFormat = "*2\r\n$4\r\nsync\r\n$%d\r\n%s\r\n" //sync logid
+	fullSyncCmd       = []byte("*1\r\n$8\r\nfullsync\r\n")                               //fullsync
+	syncCmdFormat     = "*2\r\n$4\r\nsync\r\n$%d\r\n%s\r\n"                              //sync logid
+	replconfCmdFormat = "*3\r\n$8\r\nreplconf\r\n$14\r\nlistening-port\r\n$%d\r\n%s\r\n" //replconf listening-port port
 )
 
+func (m *master) replConf() error {
+	_, port, err := net.SplitHostPort(m.app.cfg.Addr)
+	if err != nil {
+		return err
+	}
+
+	cmd := hack.Slice(fmt.Sprintf(replconfCmdFormat, len(port), port))
+
+	if _, err := m.conn.Write(cmd); err != nil {
+		return err
+	}
+
+	if s, err := ReadStatus(m.rb); err != nil {
+		return err
+	} else if strings.ToLower(s) != "ok" {
+		return fmt.Errorf("not ok but %s", s)
+	}
+
+	return nil
+}
+
 func (m *master) fullSync() error {
 	log.Info("begin full sync")
 
@@ -227,6 +262,17 @@ func (m *master) sync() error {
 
 	buf := m.syncBuf.Bytes()
 
+	if len(buf) < 8 {
+		return fmt.Errorf("inavlid sync size %d", len(buf))
+	}
+
+	m.app.info.Replication.MasterLastLogID.Set(num.BytesToUint64(buf))
+
+	var t bytes.Buffer
+	m.app.info.dumpReplication(&t)
+
+	buf = buf[8:]
+
 	if len(buf) == 0 {
 		return nil
 	}
@@ -284,24 +330,41 @@ func (app *App) tryReSlaveof() error {
 }
 
 func (app *App) addSlave(c *client) {
+	addr := c.slaveListeningAddr
+
 	app.slock.Lock()
 	defer app.slock.Unlock()
 
-	app.slaves[c] = struct{}{}
+	app.slaves[addr] = c
 }
 
-func (app *App) removeSlave(c *client) {
+func (app *App) removeSlave(c *client, activeQuit bool) {
+	addr := c.slaveListeningAddr
+
 	app.slock.Lock()
 	defer app.slock.Unlock()
 
-	if _, ok := app.slaves[c]; ok {
-		delete(app.slaves, c)
-		log.Info("remove slave %s", c.remoteAddr)
+	if _, ok := app.slaves[addr]; ok {
+		delete(app.slaves, addr)
+		log.Info("remove slave %s", addr)
+		if activeQuit {
+			asyncNotifyUint64(app.slaveSyncAck, c.lastLogID)
+		}
+	}
+}
+
+func (app *App) slaveAck(c *client) {
+	addr := c.slaveListeningAddr
+
+	app.slock.Lock()
+	defer app.slock.Unlock()
+
+	if _, ok := app.slaves[addr]; !ok {
+		//slave not add
+		return
 	}
 
-	if c.ack != nil {
-		asyncNotifyUint64(c.ack.ch, c.lastLogID)
-	}
+	asyncNotifyUint64(app.slaveSyncAck, c.lastLogID)
 }
 
 func asyncNotifyUint64(ch chan uint64, v uint64) {
@@ -317,51 +380,40 @@ func (app *App) publishNewLog(l *rpl.Log) {
 		return
 	}
 
-	ss := make([]*client, 0, 4)
+	app.info.Replication.PubLogNum.Add(1)
+
 	app.slock.Lock()
 
+	total := (len(app.slaves) + 1) / 2
+	if app.cfg.Replication.WaitMaxSlaveAcks > 0 {
+		total = num.MinInt(total, app.cfg.Replication.WaitMaxSlaveAcks)
+	}
+
+	n := 0
 	logId := l.ID
-	for s, _ := range app.slaves {
-		if s.lastLogID >= logId {
+	for _, s := range app.slaves {
+		if s.lastLogID == logId {
 			//slave has already owned this log
-			ss = []*client{}
-			break
-		} else {
-			ss = append(ss, s)
+			n++
+		} else if s.lastLogID > logId {
+			log.Error("invalid slave %s, lastlogid %d > %d", s.slaveListeningAddr, s.lastLogID, logId)
 		}
 	}
 
 	app.slock.Unlock()
 
-	if len(ss) == 0 {
+	if n >= total {
+		//at least total slaves have owned this log
 		return
 	}
 
 	startTime := time.Now()
-
-	ack := &syncAck{
-		logId, make(chan uint64, len(ss)),
-	}
-
-	for _, s := range ss {
-		s.ack = ack
-	}
-
-	total := (len(ss) + 1) / 2
-	if app.cfg.Replication.WaitMaxSlaveAcks > 0 {
-		total = num.MinInt(total, app.cfg.Replication.WaitMaxSlaveAcks)
-	}
-
 	done := make(chan struct{}, 1)
 	go func(total int) {
-		n := 0
-		for i := 0; i < len(ss); i++ {
-			id := <-ack.ch
-			if id > logId {
-				n++
-				if n >= total {
-					break
-				}
+		for i := 0; i < total; i++ {
+			id := <-app.slaveSyncAck
+			if id < logId {
+				log.Info("some slave may close with last logid %d < %d", id, logId)
 			}
 		}
 		done <- struct{}{}
@@ -374,6 +426,6 @@ func (app *App) publishNewLog(l *rpl.Log) {
 	}
 
 	stopTime := time.Now()
-	atomic.AddInt64(&app.info.Replication.PubLogNum, 1)
-	atomic.AddInt64(&app.info.Replication.PubLogTotalTime, stopTime.Sub(startTime).Nanoseconds()/1e6)
+	app.info.Replication.PubLogAckNum.Add(1)
+	app.info.Replication.PubLogTotalAckTime.Add(stopTime.Sub(startTime))
 }
diff --git a/server/util.go b/server/util.go
index abd6536..15e6d7b 100644
--- a/server/util.go
+++ b/server/util.go
@@ -9,9 +9,10 @@ import (
 )
 
 var (
-	errArrayFormat = errors.New("bad array format")
-	errBulkFormat  = errors.New("bad bulk string format")
-	errLineFormat  = errors.New("bad response line format")
+	errArrayFormat  = errors.New("bad array format")
+	errBulkFormat   = errors.New("bad bulk string format")
+	errLineFormat   = errors.New("bad response line format")
+	errStatusFormat = errors.New("bad status format")
 )
 
 func ReadLine(rb *bufio.Reader) ([]byte, error) {
@@ -54,9 +55,26 @@ func ReadBulkTo(rb *bufio.Reader, w io.Writer) error {
 				return errBulkFormat
 			}
 		}
+	} else if l[0] == '-' {
+		return errors.New(string(l[1:]))
 	} else {
 		return errBulkFormat
 	}
 
 	return nil
 }
+
+func ReadStatus(rb *bufio.Reader) (string, error) {
+	l, err := ReadLine(rb)
+	if err != nil {
+		return "", err
+	} else if len(l) == 0 {
+		return "", errStatusFormat
+	} else if l[0] == '+' {
+		return string(l[1:]), nil
+	} else if l[0] == '-' {
+		return "", errors.New(string(l[1:]))
+	} else {
+		return "", errStatusFormat
+	}
+}