diff --git a/pymycobot/common.py b/pymycobot/common.py
index 28a2cb2..dc2e506 100644
--- a/pymycobot/common.py
+++ b/pymycobot/common.py
@@ -1199,6 +1199,9 @@ def read(self, genre, method=None, command=None, _class=None, timeout=None, real
                 break
             elif len(datas) == 2:
                 data_len = struct.unpack("b", data)[0]
+                if data_len < 0 or data_len > 30:
+                    data_len = -1
+                    continue
                 datas += data
             elif len(datas) > 2 and data_len > 0:
                 datas += data
diff --git a/pymycobot/error.py b/pymycobot/error.py
index dd8ea94..782f9df 100644
--- a/pymycobot/error.py
+++ b/pymycobot/error.py
@@ -418,7 +418,7 @@ def public_check(
                 check_0_or_1(
                     parameter,
                     value,
-                    [19, 22, 23, 33],
+                    [19, 22, 23, 33, 39],
                     value_type,
                     exception_class,
                     int,
diff --git a/pymycobot/mycobot280.py b/pymycobot/mycobot280.py
index fcc2482..40573e0 100644
--- a/pymycobot/mycobot280.py
+++ b/pymycobot/mycobot280.py
@@ -150,12 +150,18 @@ def _res(self, real_command, has_reply, genre):
             data = self._read(genre)
         else:
             try_count = 0
+            expected_genre = genre
             while try_count < 3:
+                self._serial_port.reset_input_buffer()
                 self._write(self._flatten(real_command))
                 data = self._read(genre)
-                if data is not None and data != b'':
-                    break
-                try_count += 1
+                if not data or len(data) < 4:
+                    try_count += 1
+                    continue
+                if data[3] != expected_genre:
+                    try_count += 1
+                    continue
+                break
             else:
                 return -1
         if genre == ProtocolCode.SET_SSID_PWD:
diff --git a/pymycobot/mycobot280socket.py b/pymycobot/mycobot280socket.py
index 40f7d45..21f0132 100644
--- a/pymycobot/mycobot280socket.py
+++ b/pymycobot/mycobot280socket.py
@@ -140,12 +140,17 @@ def _res(self, real_command, has_reply, genre):
             data = self._read(genre, method='socket')
         else:
             try_count = 0
+            expected_genre = genre
             while try_count < 3:
                 self._write(self._flatten(real_command), "socket")
                 data = self._read(genre, method='socket')
-                if data is not None and data != b'':
-                    break
-                try_count += 1
+                if not data or len(data) < 4:
+                    try_count += 1
+                    continue
+                if data[3] != expected_genre:
+                    try_count += 1
+                    continue
+                break
             else:
                 return -1
         if genre == ProtocolCode.SET_SSID_PWD: