diff --git a/src/main.go b/src/main.go
index d7775d6..7c53867 100644
--- a/src/main.go
+++ b/src/main.go
@@ -18,6 +18,11 @@ import (
 	"github.com/sunbk201/ua3f/log"
 )
 
+var (
+	ErrInvalidSocksVersion = errors.New("invalid socks version")
+	ErrInvalidSocksCmd     = errors.New("invalid socks cmd")
+)
+
 var version = "0.7.3"
 var payload string
 var uaPattern string
@@ -90,17 +95,20 @@ func process(client net.Conn) {
 		client.Close()
 		return
 	}
-	target, destAddrPort, err := Socks5Connect(client)
+	destAddrPort, err := ParseSocks5Request(client)
 	if err != nil {
-		// UDP
 		if strings.Contains(err.Error(), "UDP Associate") {
 			Socks5UDP(client)
 			client.Close()
 			return
-		} else if strings.Contains(err.Error(), "connection timed out") {
-			logrus.Debug("Connect timeout: ", err)
+		} else {
+			logrus.Debug(fmt.Sprintf("[%s][%s] ParseSocks5Request failed: %s", client.RemoteAddr().String(), destAddrPort, err.Error()))
+			client.Close()
 			return
 		}
+	}
+	target, err := Socks5Connect(client, destAddrPort)
+	if err != nil {
 		logrus.Debug("Connect failed: ", err)
 		client.Close()
 		return
@@ -112,7 +120,7 @@ func Socks5Auth(client net.Conn) (err error) {
 	buf := make([]byte, 256)
 	n, err := io.ReadFull(client, buf[:2])
 	if n != 2 {
-		if err == io.EOF {
+		if errors.Is(err, io.EOF) {
 			logrus.Warn(fmt.Sprintf("[%s][Auth] read EOF", client.RemoteAddr().String()))
 		} else {
 			logrus.Error(fmt.Sprintf("[%s][Auth] read header: %s", client.RemoteAddr().String(), err.Error()))
@@ -122,7 +130,7 @@ func Socks5Auth(client net.Conn) (err error) {
 	ver, nMethods := int(buf[0]), int(buf[1])
 	if ver != 5 {
 		logrus.Error(fmt.Sprintf("[%s][Auth] invalid ver", client.RemoteAddr().String()))
-		return errors.New("invalid version")
+		return ErrInvalidSocksVersion
 	}
 	n, err = io.ReadFull(client, buf[:nMethods])
 	if n != nMethods {
@@ -264,64 +272,72 @@ func Socks5UDP(client net.Conn) {
 	udpserver.Close()
 }
 
-func Socks5Connect(client net.Conn) (net.Conn, string, error) {
-	buf := make([]byte, 256)
-	n, err := io.ReadFull(client, buf[:4])
-	if n != 4 {
-		return nil, "", errors.New("read header:" + err.Error())
-	}
-	ver, cmd, _, atyp := buf[0], buf[1], buf[2], buf[3]
-	if ver != 5 {
-		return nil, "", errors.New("invalid ver")
-	}
-	if cmd == 3 {
-		return nil, "", errors.New("UDP Associate")
-	}
-	if cmd != 1 {
-		return nil, "", errors.New("invalid cmd, only support connect")
-	}
-	addr := ""
-	switch atyp {
-	case 1:
-		n, err = io.ReadFull(client, buf[:4])
-		if n != 4 {
-			return nil, "", errors.New("invalid IPv4:" + err.Error())
-		}
-		addr = fmt.Sprintf("%d.%d.%d.%d", buf[0], buf[1], buf[2], buf[3])
-	case 3:
-		n, err = io.ReadFull(client, buf[:1])
-		if n != 1 {
-			return nil, "", errors.New("invalid hostname:" + err.Error())
-		}
-		addrLen := int(buf[0])
-		n, err = io.ReadFull(client, buf[:addrLen])
-		if n != addrLen {
-			return nil, "", errors.New("invalid hostname:" + err.Error())
-		}
-		addr = string(buf[:addrLen])
-	case 4:
-		return nil, "", errors.New("IPv6: no supported yet")
-	default:
-		return nil, "", errors.New("invalid atyp")
-	}
-	n, err = io.ReadFull(client, buf[:2])
-	if n != 2 {
-		return nil, "", errors.New("read port:" + err.Error())
-	}
-	port := binary.BigEndian.Uint16(buf[:2])
-	destAddrPort := fmt.Sprintf("%s:%d", addr, port)
+func Socks5Connect(client net.Conn, destAddrPort string) (target net.Conn, err error) {
 	logrus.Debug(fmt.Sprintf("Connecting %s", destAddrPort))
 	dest, err := net.Dial("tcp", destAddrPort)
 	if err != nil {
-		return nil, destAddrPort, errors.New("dial dst:" + err.Error())
+		return nil, err
 	}
 	logrus.Debug(fmt.Sprintf("Connected %s", destAddrPort))
 	_, err = client.Write([]byte{0x05, 0x00, 0x00, 0x01, 0, 0, 0, 0, 0, 0})
 	if err != nil {
 		dest.Close()
-		return nil, destAddrPort, errors.New("write rsp:" + err.Error())
+		return nil, err
 	}
-	return dest, destAddrPort, nil
+	return dest, nil
+}
+
+func ParseSocks5Request(client net.Conn) (destAddrPort string, err error) {
+	buf := make([]byte, 256)
+	if _, err = io.ReadFull(client, buf[:4]); err != nil {
+		err = fmt.Errorf("read header: %w", err)
+		return
+	}
+	ver, cmd, _, atyp := buf[0], buf[1], buf[2], buf[3]
+	if ver != 5 {
+		err = ErrInvalidSocksVersion
+		return
+	}
+	if cmd == 3 {
+		return "", errors.New("UDP Associate")
+	} else if cmd != 1 {
+		err = ErrInvalidSocksCmd
+		return
+	}
+	var addr string
+	switch atyp {
+	case 1:
+		if _, err = io.ReadFull(client, buf[:4]); err != nil {
+			err = fmt.Errorf("invalid IPv4: %w", err)
+			return
+		}
+		addr = fmt.Sprintf("%d.%d.%d.%d", buf[0], buf[1], buf[2], buf[3])
+	case 3:
+		if _, err = io.ReadFull(client, buf[:1]); err != nil {
+			err = fmt.Errorf("invalid hostname: %w", err)
+			return
+		}
+		addrLen := int(buf[0])
+		if _, err = io.ReadFull(client, buf[:addrLen]); err != nil {
+			err = fmt.Errorf("invalid hostname: %w", err)
+			return
+		}
+		addr = string(buf[:addrLen])
+	case 4:
+		err = errors.New("IPv6: no supported yet")
+		return
+	default:
+		err = errors.New("invalid atyp")
+		return
+	}
+
+	if _, err = io.ReadFull(client, buf[:2]); err != nil {
+		err = fmt.Errorf("read port: %w", err)
+		return
+	}
+	port := binary.BigEndian.Uint16(buf[:2])
+	destAddrPort = fmt.Sprintf("%s:%d", addr, port)
+	return destAddrPort, nil
 }
 
 func Socks5Forward(client, target net.Conn, destAddrPort string) {