diff --git a/client/client.go b/client/client.go
new file mode 100644
index 0000000..c826db6
--- /dev/null
+++ b/client/client.go
@@ -0,0 +1,305 @@
+package client
+
+import (
+	"context"
+	"fmt"
+	"reflect"
+	"sync"
+	"time"
+
+	logging "git.loafle.net/commons/logging-go"
+	"git.loafle.net/commons/rpc-go/protocol"
+	"git.loafle.net/commons/rpc-go/registry"
+)
+
+var uint64Type = reflect.TypeOf(uint64(0))
+
+type Client struct {
+	Codec      protocol.ClientCodec
+	RPCInvoker registry.RPCInvoker
+
+	stopChan chan struct{}
+	stopWg   sync.WaitGroup
+
+	requestID        uint64
+	requestQueueChan chan *requestState
+
+	pendingRequests sync.Map
+}
+
+func (c *Client) Start(readChan <-chan []byte, writeChan chan<- []byte) error {
+	if c.stopChan != nil {
+		return fmt.Errorf("Client: already running. Stop it before starting it again")
+	}
+
+	if nil == c.Codec {
+		return fmt.Errorf("Client: Codec is not valid")
+	}
+
+	c.stopChan = make(chan struct{})
+
+	c.stopWg.Add(1)
+	go c.handleClient(readChan, writeChan)
+
+	return nil
+}
+
+func (c *Client) Stop(ctx context.Context) error {
+	if c.stopChan == nil {
+		return fmt.Errorf("Client: must be started before stopping it")
+	}
+	close(c.stopChan)
+	c.stopWg.Wait()
+	c.stopChan = nil
+
+	return nil
+}
+
+func (c *Client) Send(method string, params ...interface{}) error {
+	rs, err := c.internalSend(false, nil, method, params...)
+	if nil != err {
+		return err
+	}
+
+	defer releaseRequestState(rs)
+	select {
+	case <-rs.doneChan:
+		if nil != rs.clientError {
+			return rs.clientError
+		}
+	}
+	return nil
+}
+
+func (c *Client) Call(result interface{}, method string, params ...interface{}) error {
+	return c.CallTimeout(10, result, method, params...)
+}
+
+func (c *Client) CallTimeout(timeout time.Duration, result interface{}, method string, params ...interface{}) error {
+	rs, err := c.internalSend(true, result, method, params...)
+	if nil != err {
+		return err
+	}
+
+	t := retainTimer(timeout)
+	defer func() {
+		releaseRequestState(rs)
+		releaseTimer(t)
+	}()
+
+	select {
+	case <-rs.doneChan:
+		result = rs.result
+		return rs.clientError
+	case <-t.C:
+		rs.cancel()
+		return newError(method, params, fmt.Errorf("Timeout"))
+	}
+}
+
+func (c *Client) getRequestID() uint64 {
+	c.requestID++
+	return c.requestID
+}
+
+func (c *Client) internalSend(hasResponse bool, result interface{}, method string, params ...interface{}) (*requestState, error) {
+	rs := retainRequestState()
+
+	rs.method = method
+	rs.params = params
+	rs.doneChan = make(chan *requestState, 1)
+	if hasResponse {
+		rs.id = c.getRequestID()
+		rs.result = result
+	}
+
+	select {
+	case c.requestQueueChan <- rs:
+		return rs, nil
+	default:
+		if !hasResponse {
+			releaseRequestState(rs)
+			return nil, newError(method, params, fmt.Errorf("Request Queue overflow"))
+		}
+		select {
+		case oldRS := <-c.requestQueueChan:
+			if nil != oldRS.doneChan {
+				oldRS.setError(fmt.Errorf("Request Queue overflow"))
+				oldRS.done()
+			} else {
+				releaseRequestState(oldRS)
+			}
+		default:
+		}
+		select {
+		case c.requestQueueChan <- rs:
+			return rs, nil
+		default:
+			releaseRequestState(rs)
+			return nil, newError(method, params, fmt.Errorf("Request Queue overflow"))
+		}
+	}
+}
+
+func (c *Client) handleClient(readChan <-chan []byte, writeChan chan<- []byte) {
+	defer func() {
+		c.stopWg.Done()
+	}()
+
+	stopChan := make(chan struct{})
+	sendDoneChan := make(chan error)
+	receiveDoneChan := make(chan error)
+
+	go c.handleSend(stopChan, sendDoneChan, writeChan)
+	go c.handleReceive(stopChan, receiveDoneChan, readChan)
+
+	select {
+	case <-sendDoneChan:
+		close(stopChan)
+		<-receiveDoneChan
+	case <-receiveDoneChan:
+		close(stopChan)
+		<-sendDoneChan
+	case <-c.stopChan:
+		close(stopChan)
+		<-sendDoneChan
+		<-receiveDoneChan
+	}
+}
+
+func (c *Client) handleSend(stopChan <-chan struct{}, doneChan chan<- error, writeChan chan<- []byte) {
+	var (
+		rs      *requestState
+		id      interface{}
+		message []byte
+		err     error
+		ok      bool
+	)
+
+	defer func() {
+		doneChan <- err
+	}()
+
+LOOP:
+	for {
+		select {
+		case rs, ok = <-c.requestQueueChan:
+			if !ok {
+				return
+			}
+			if rs.isCanceled() {
+				if nil != rs.doneChan {
+					rs.done()
+				} else {
+					releaseRequestState(rs)
+				}
+				continue LOOP
+			}
+
+			id = nil
+			if 0 < rs.id {
+				id = rs.id
+			}
+			message, err = c.Codec.NewRequest(rs.method, rs.params, id)
+			if nil != err {
+				rs.setError(err)
+				rs.done()
+				continue LOOP
+			}
+
+			select {
+			case writeChan <- message:
+			default:
+				rs.setError(fmt.Errorf("Client: cannot send request"))
+				rs.done()
+				continue LOOP
+			}
+
+			if 0 < rs.id {
+				c.pendingRequests.Store(rs.id, rs)
+			}
+		case <-c.stopChan:
+			return
+		}
+	}
+}
+
+func (c *Client) handleReceive(stopChan <-chan struct{}, doneChan chan<- error, readChan <-chan []byte) {
+	var (
+		message []byte
+		err     error
+		ok      bool
+	)
+
+	defer func() {
+		doneChan <- err
+	}()
+
+LOOP:
+	for {
+		select {
+		case message, ok = <-readChan:
+			if !ok {
+				return
+			}
+			resCodec, err := c.Codec.NewResponse(message)
+			if nil != err {
+				continue LOOP
+			}
+			if nil == resCodec.ID() {
+				// notification
+				notiCodec, err := resCodec.Notification()
+				if nil != err {
+					logging.Logger().Warnf("Client: notification error %v", err)
+					continue LOOP
+				}
+
+				c.stopWg.Add(1)
+				go c.handleNotification(notiCodec)
+			} else {
+				// response
+				c.stopWg.Add(1)
+				go c.handleResponse(resCodec)
+			}
+		case <-stopChan:
+			return
+		}
+	}
+
+}
+
+func (c *Client) handleResponse(resCodec protocol.ClientResponseCodec) {
+	defer func() {
+		c.stopWg.Done()
+	}()
+	id := reflect.ValueOf(resCodec.ID()).Convert(uint64Type).Uint()
+	_rs, ok := c.pendingRequests.Load(id)
+	if !ok {
+		logging.Logger().Warnf("Client: unexpected ID=[%d] obtained from server", id)
+		return
+	}
+	rs := _rs.(*requestState)
+	rs.setError(resCodec.Error())
+	err := resCodec.Result(rs.result)
+	if nil != err {
+		rs.setError(err)
+	}
+
+	rs.done()
+}
+
+func (c *Client) handleNotification(notiCodec protocol.ClientNotificationCodec) {
+	defer func() {
+		c.stopWg.Done()
+	}()
+
+	if nil == c.RPCInvoker {
+		logging.Logger().Warnf("Client: received notification method[%s] but RPC Invoker is not exist", notiCodec.Method())
+		return
+	}
+
+	_, err := c.RPCInvoker.Invoke(notiCodec)
+	if nil != err {
+		logging.Logger().Errorf("Client: invoking of notification method[%s] has been failed %v", notiCodec.Method(), err)
+	}
+}
diff --git a/client/error.go b/client/error.go
new file mode 100644
index 0000000..ec9ad8e
--- /dev/null
+++ b/client/error.go
@@ -0,0 +1,20 @@
+package client
+
+func newError(method string, params []interface{}, err error) *Error {
+	return &Error{
+		Method: method,
+		Params: params,
+		Err:    err,
+	}
+}
+
+type Error struct {
+	Method string
+	Params []interface{}
+
+	Err error
+}
+
+func (e *Error) Error() string {
+	return e.Err.Error()
+}
diff --git a/client/request-state.go b/client/request-state.go
new file mode 100644
index 0000000..fe4b034
--- /dev/null
+++ b/client/request-state.go
@@ -0,0 +1,93 @@
+package client
+
+import (
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+type requestState struct {
+	id          uint64
+	method      string
+	params      []interface{}
+	result      interface{}
+	clientError *Error
+	doneChan    chan *requestState
+
+	canceled atomic.Value
+}
+
+func (rs *requestState) done() {
+	select {
+	case rs.doneChan <- rs:
+	default:
+	}
+}
+
+func (rs *requestState) cancel() {
+	rs.canceled.Store(true)
+}
+
+func (rs *requestState) isCanceled() bool {
+	v := rs.canceled.Load()
+	if nil == v {
+		return false
+	}
+	vv := v.(bool)
+
+	return vv
+}
+
+func (rs *requestState) setError(err error) {
+	rs.clientError = newError(rs.method, rs.params, err)
+}
+
+var requestStatePool sync.Pool
+
+func retainRequestState() *requestState {
+	v := requestStatePool.Get()
+	if v == nil {
+		return &requestState{}
+	}
+	return v.(*requestState)
+}
+
+func releaseRequestState(rs *requestState) {
+	rs.id = 0
+	rs.method = ""
+	rs.params = nil
+	rs.result = nil
+	rs.clientError = nil
+	rs.doneChan = nil
+	rs.canceled.Store(false)
+
+	requestStatePool.Put(rs)
+}
+
+var timerPool sync.Pool
+
+func retainTimer(timeout time.Duration) *time.Timer {
+	tv := timerPool.Get()
+	if tv == nil {
+		return time.NewTimer(timeout)
+	}
+
+	t := tv.(*time.Timer)
+	if t.Reset(timeout) {
+		panic("Client: Active timer trapped into retainTimer()")
+	}
+	return t
+}
+
+func releaseTimer(t *time.Timer) {
+	if !t.Stop() {
+		// Collect possibly added time from the channel
+		// if timer has been stopped and nobody collected its' value.
+		select {
+		case <-t.C:
+		default:
+		}
+	}
+
+	timerPool.Put(t)
+}