diff --git a/code/network/network.go b/code/network/network.go
index f5ed4bf..e487f71 100644
--- a/code/network/network.go
+++ b/code/network/network.go
@@ -3,13 +3,16 @@ package network
 import (
 	"bytes"
 	"encoding/binary"
+	"encoding/hex"
 	"errors"
+	"hash/crc32"
 	"io"
 	"math"
 	"net"
 	"sync"
 	"time"
 
+	"github.com/lwch/logging"
 	"google.golang.org/protobuf/proto"
 )
 
@@ -21,7 +24,7 @@ type Conn struct {
 	c         net.Conn
 	lockRead  sync.Mutex
 	lockWrite sync.Mutex
-	sizeRead  [4]byte
+	sizeRead  [6]byte
 }
 
 // NewConn create connection
@@ -34,16 +37,6 @@ func (c *Conn) Close() {
 	c.c.Close()
 }
 
-func sum(data []byte) uint16 {
-	tmp := make([]uint16, len(data)/2)
-	binary.Read(bytes.NewReader(data), binary.BigEndian, tmp)
-	var ret uint16
-	for _, v := range tmp {
-		ret += v
-	}
-	return ret
-}
-
 // ReadMessage read message with timeout
 func (c *Conn) ReadMessage(timeout time.Duration) (*Msg, error) {
 	c.lockRead.Lock()
@@ -54,13 +47,14 @@ func (c *Conn) ReadMessage(timeout time.Duration) (*Msg, error) {
 		return nil, err
 	}
 	size := binary.BigEndian.Uint16(c.sizeRead[:])
-	enc := binary.BigEndian.Uint16(c.sizeRead[2:])
+	enc := binary.BigEndian.Uint32(c.sizeRead[2:])
 	buf := make([]byte, size)
 	_, err = io.ReadFull(c.c, buf)
 	if err != nil {
 		return nil, err
 	}
-	if sum(buf) != enc {
+	if crc32.ChecksumIEEE(buf) != enc {
+		logging.Info("sum=%d, enc=%d\n%s", crc32.ChecksumIEEE(buf), enc, hex.Dump(buf))
 		return nil, errChecksum
 	}
 	var msg Msg
@@ -84,7 +78,7 @@ func (c *Conn) WriteMessage(m *Msg, timeout time.Duration) error {
 	}
 	buf := make([]byte, len(data)+len(c.sizeRead))
 	binary.BigEndian.PutUint16(buf, uint16(len(data)))
-	binary.BigEndian.PutUint16(buf[2:], sum(data))
+	binary.BigEndian.PutUint32(buf[2:], crc32.ChecksumIEEE(data))
 	copy(buf[len(c.sizeRead):], data)
 	c.c.SetWriteDeadline(time.Now().Add(timeout))
 	_, err = io.Copy(c.c, bytes.NewReader(buf))