diff --git a/obfssh_scp/scp.go b/obfssh_scp/scp.go
index f3e4d79..783d6a6 100644
--- a/obfssh_scp/scp.go
+++ b/obfssh_scp/scp.go
@@ -3,6 +3,7 @@ package main
 import (
 	"flag"
 	"fmt"
+	"github.com/bgentry/speakeasy"
 	"github.com/fangdingjun/obfssh"
 	"github.com/kr/fs"
 	"github.com/pkg/sftp"
@@ -24,7 +25,16 @@ func main() {
 	var recursive bool
 	var obfsMethod, obfsKey string
 	var disableObfsAfterHandshake bool
+	var debug bool
 
+	flag.Usage = func() {
+		fmt.Printf("Usage: \n\t%s [options] user@host:path local\n\tor\n\t%s [options] local... user@host:path\n", os.Args[0], os.Args[0])
+
+		fmt.Printf("Options:\n\n")
+
+		flag.PrintDefaults()
+	}
+	flag.BoolVar(&debug, "d", false, "verbose mode")
 	flag.StringVar(&port, "p", "22", "port")
 	flag.StringVar(&user, "l", os.Getenv("USER"), "user")
 	flag.StringVar(&pass, "pw", "", "password")
@@ -35,10 +45,15 @@ func main() {
 	flag.BoolVar(&disableObfsAfterHandshake, "disable_obfs_after_handshake", false, "disable obfs after handshake")
 	flag.Parse()
 
+	if debug {
+		obfssh.SSHLogLevel = obfssh.DEBUG
+	}
+
 	args := flag.Args()
 
 	if len(args) < 2 {
-		fmt.Printf("Usage: \n\tscp user@host:path local\n\tor\n\tscp local... user@host:path\n")
+		//fmt.Printf("Usage: \n\tscp user@host:path local\n\tor\n\tscp local... user@host:path\n")
+		flag.Usage()
 		os.Exit(1)
 	}
 
@@ -60,7 +75,9 @@ func main() {
 	}
 	ss2 := strings.SplitN(r1, ":", 2)
 	if len(ss2) != 2 {
-		log.Fatal("Usage: \n\tscp user@host:path local\n\tor\n\tscp local... user@host:path")
+		//log.Fatal("Usage: \n\tscp user@host:path local\n\tor\n\tscp local... user@host:path")
+		flag.Usage()
+		os.Exit(1)
 	}
 	host = ss2[0]
 	path = ss2[1]
@@ -72,9 +89,14 @@ func main() {
 		var pkeys []ssh.Signer
 		if aconn, err := net.Dial("unix", os.Getenv("SSH_AUTH_SOCK")); err == nil {
 			//auths = append(auths, ssh.PublicKeysCallback(agent.NewClient(aconn).Signers))
-			if signers, err := agent.NewClient(aconn).Signers(); err != nil {
+			if signers, err := agent.NewClient(aconn).Signers(); err == nil {
+				debuglog("add private key from agent")
 				pkeys = append(pkeys, signers...)
+			} else {
+				debuglog("get key from agent failed: %s", err)
 			}
+		} else {
+			debuglog("dial to agent failed: %s", err)
 		}
 
 		home := os.Getenv("HOME")
@@ -88,29 +110,44 @@ func main() {
 			k1 := filepath.Join(home, f)
 			if pemBytes, err := ioutil.ReadFile(k1); err == nil {
 				if priKey, err := ssh.ParsePrivateKey(pemBytes); err == nil {
-					//log.Printf("add pri...")
 					//auths = append(auths, ssh.PublicKeys(priKey))
 					pkeys = append(pkeys, priKey)
+					debuglog("add private key %s", k1)
+				} else {
+					debuglog("parse private key failed: %s", err)
 				}
 			}
 
 		}
+
 		if len(pkeys) != 0 {
+			debuglog("totol %d private keys", len(pkeys))
 			auths = append(auths, ssh.PublicKeys(pkeys...))
 		}
 	}
 
 	if pass != "" {
+		debuglog("add password auth")
 		auths = append(auths, ssh.Password(pass))
+	} else {
+		debuglog("add keyboard interactive")
+		auths = append(auths,
+			ssh.RetryableAuthMethod(ssh.PasswordCallback(passwordAuth), 3))
 	}
 
 	if key != "" {
 		if buf, err := ioutil.ReadFile(key); err == nil {
 			if p, err := ssh.ParsePrivateKey(buf); err == nil {
+				debuglog("add private key: %s", key)
 				auths = append(auths, ssh.PublicKeys(p))
+			} else {
+				debuglog("parse private key failed: %s", err)
 			}
+		} else {
+			debuglog("read private key failed: %s", err)
 		}
 	}
+
 	config := &ssh.ClientConfig{
 		User:    user,
 		Auth:    auths,
@@ -166,19 +203,25 @@ func main() {
 		}
 
 		if !st.Mode().IsDir() {
-			if st1.Mode().IsDir() {
+			if st1 != nil && st1.Mode().IsDir() {
+				// to local directory
 				bname := filepath.Base(path)
 				localFile = filepath.Join(localFile, bname)
 			}
+
+			debuglog("transfer remote to local, %s -> %s", path, localFile)
+
 			if err := get(sftpConn, path, localFile); err != nil {
 				log.Fatal(err)
 			}
+			debuglog("done")
 			return
 		}
 
 		// recursive download
 		rget(sftpConn, path, localFile)
 
+		debuglog("done")
 		return
 	}
 
@@ -199,14 +242,14 @@ func main() {
 
 		// local file not exists
 		if err != nil {
-			log.Println(err)
+			debuglog("%s", err)
 			continue
 		}
 
 		// directory
 		if st.Mode().IsDir() {
 			if !recursive {
-				log.Printf("omit directory %s", localFile)
+				debuglog("omit directory %s", localFile)
 				continue
 			}
 			// transfer directory
@@ -219,16 +262,18 @@ func main() {
 		// file
 		remoteFile := filepath.Join(path, filepath.Base(localFile))
 		if err := put(sftpConn, localFile, remoteFile); err != nil {
-			log.Printf("upload %s failed: %s", localFile, err.Error())
+			debuglog("upload %s failed: %s", localFile, err.Error())
 		}
 	}
 
 }
 
 func get(sftpConn *sftp.Client, remoteFile, localFile string) error {
+
+	debuglog("download %s -> %s", remoteFile, localFile)
+
 	fp, err := sftpConn.Open(remoteFile)
 	if err != nil {
-		//log.Fatal(err)
 		return err
 	}
 
@@ -236,45 +281,56 @@ func get(sftpConn *sftp.Client, remoteFile, localFile string) error {
 
 	fp1, err := os.OpenFile(localFile, syscall.O_WRONLY|syscall.O_CREAT|syscall.O_TRUNC, 0644)
 	if err != nil {
-		//log.Fatal(err)
 		return err
 	}
 
 	defer fp1.Close()
 
-	_, err = io.Copy(fp1, fp)
+	//_, err = io.Copy(fp1, fp)
+	err = copyFile(fp1, fp)
 	if err != nil {
-		//log.Fatal(err)
 		return err
 	}
 
 	// set permission and modtime
-	st, _ := sftpConn.Stat(remoteFile)
+
+	st, err := sftpConn.Stat(remoteFile)
+	if err != nil {
+		return err
+	}
+
 	if err := os.Chmod(localFile, st.Mode().Perm()); err != nil {
-		//log.Println(err)
 		return err
 	}
+
 	if err := os.Chtimes(localFile, st.ModTime(), st.ModTime()); err != nil {
-		//log.Println(err)
 		return err
 	}
+
+	debuglog("done")
+
 	return nil
 }
 
 func put(sftpConn *sftp.Client, localFile, remoteFile string) error {
+	debuglog("upload %s -> %s", localFile, remoteFile)
+
 	fpw, err := sftpConn.OpenFile(remoteFile, syscall.O_WRONLY|syscall.O_CREAT|syscall.O_TRUNC)
 	if err != nil {
-		//log.Fatal(err)
 		return err
 	}
+
 	defer fpw.Close()
+
 	fpr, err := os.Open(localFile)
 	if err != nil {
-		//log.Fatal(err)
 		return err
 	}
+
 	defer fpr.Close()
-	_, err = io.Copy(fpw, fpr)
+
+	//_, err = io.Copy(fpw, fpr)
+	err = copyFile(fpw, fpr)
 	if err != nil {
 		//log.Fatal(err)
 		return err
@@ -282,14 +338,17 @@ func put(sftpConn *sftp.Client, localFile, remoteFile string) error {
 
 	// set permission and modtime
 	st, _ := os.Stat(localFile)
+
 	if err := sftpConn.Chmod(remoteFile, st.Mode().Perm()); err != nil {
-		//log.Println(err)
 		return err
 	}
+
 	if err := sftpConn.Chtimes(remoteFile, st.ModTime(), st.ModTime()); err != nil {
-		//log.Println(err)
 		return err
 	}
+
+	debuglog("done")
+
 	return nil
 }
 
@@ -297,45 +356,62 @@ func rput(sftpConn *sftp.Client, localDir, remoteDir string) error {
 	walker := fs.Walk(localDir)
 	for walker.Step() {
 		if err := walker.Err(); err != nil {
-			log.Println(err)
+			debuglog("walker error: %s", err)
 			continue
 		}
-		if st := walker.Stat(); st.Mode().IsDir() {
+
+		if st := walker.Stat(); !st.Mode().IsRegular() {
+			debuglog("skip %s", walker.Path())
 			continue
 		}
+
 		p := walker.Path()
+
 		p1 := strings.Replace(p, localDir, "", 1)
+
+		fmt.Println(strings.TrimLeft(p1, "/"))
+
 		p2 := filepath.Join(remoteDir, p1)
+
 		if err := makeDirs(p2, sftpConn); err != nil {
-			log.Println(err)
+			debuglog("make directory error: %s", err)
 			continue
 		}
 
 		if err := put(sftpConn, p, p2); err != nil {
-			log.Printf("upload %s failed: %s", p, err.Error())
+			debuglog("upload %s failed: %s", p, err.Error())
 		}
 	}
 	return nil
 }
 
 func rget(sftpConn *sftp.Client, remoteDir, localDir string) error {
+	debuglog("transfer recusive from remote to local, %s -> %s", remoteDir, localDir)
+
 	walker := sftpConn.Walk(remoteDir)
 	for walker.Step() {
 		if err := walker.Err(); err != nil {
-			log.Println(err)
+			debuglog("walk error: %s", err)
 			continue
 		}
-		if st := walker.Stat(); st.Mode().IsDir() {
+
+		if st := walker.Stat(); !st.Mode().IsRegular() {
+			debuglog("skip %s", walker.Path())
 			continue
 		}
+
 		p := walker.Path()
 		p1 := strings.Replace(p, remoteDir, "", 1)
 		p2 := filepath.Join(localDir, p1)
+
+		fmt.Println(strings.TrimLeft(p1, "/"))
+
 		if err := makeDirs(p2, fi{}); err != nil {
-			log.Println(err)
+			debuglog("make directory failed: %s", err)
 		}
+
 		if err := get(sftpConn, p, p2); err != nil {
-			log.Printf("download %s failed: %s", p, err.Error())
+			debuglog("download %s failed: %s", p, err.Error())
 		}
 	}
 	return nil
@@ -357,10 +433,13 @@ type fileInterface interface {
 }
 
 func makeDirs(p string, c fileInterface) error {
+	debuglog("make directory for %s", p)
+
 	for i := 1; i < len(p); i++ {
 		if p[i] == '/' {
 			p1 := p[:i]
 			if _, err := c.Stat(p1); err != nil {
+				debuglog("make directory %s", p1)
 				if err := c.Mkdir(p1); err != nil {
 					return err
 				}
@@ -369,3 +448,39 @@ func makeDirs(p string, c fileInterface) error {
 	}
 	return nil
 }
+
+func passwordAuth() (string, error) {
+	// read password from console
+	s, err := speakeasy.Ask("Password: ")
+	return strings.Trim(s, " \r\n"), err
+}
+
+func debuglog(format string, args ...interface{}) {
+	obfssh.Log(obfssh.DEBUG, format, args...)
+}
+
+//
+// when use pkg/sftp client transfer a big file from pkg/sftp server,
+// io.Copy while cause connection hang,
+// I don't known why,
+// use this func with smaller buffer has no problem
+//
+func copyFile(w io.Writer, r io.Reader) error {
+	buf := make([]byte, 512)
+	for {
+		n, err := r.Read(buf)
+		if n > 0 {
+			_, err1 := w.Write(buf[:n])
+			if err1 != nil {
+				return err1
+			}
+		}
+		if err != nil {
+			if err == io.EOF {
+				// trust io.EOF as success
+				return nil
+			}
+			return err
+		}
+	}
+}