diff --git a/src/modem.rs b/src/modem.rs
index 788bf39..6018de2 100644
--- a/src/modem.rs
+++ b/src/modem.rs
@@ -290,6 +290,8 @@ impl<UART: serial::Uart> Modem<UART> {
     }
 
     pub fn tcp_manual_send(&mut self, buf: &[u8]) -> Result<()> {
+       thread::sleep(Duration::from_millis(200));
+       self.serial.clear();
         self.tcp_manual_send_data(buf)
             .map(|_| ())
     }
@@ -556,8 +558,6 @@ where
             )?;
         }
         if let Ok(()) = mdm.try_connect_gprs() {
-            let device_id = "c36a72df-5bd6-4f9b-995d-059433bc3267";
-
             // When command AT+CIPQSEND=0, it is in normal sending mode. In this mode, after user
             // sends data by AT+CIPSEND, if the server receives TCP data, it will give ACK message
             // to module, and the module will respond SEND OK.
@@ -571,9 +571,8 @@ where
                     continue;
                 }
             }
-            thread::sleep(Duration::from_millis(500));
-            mdm.serial.clear();
 
+            let device_id = "c36a72df-5bd6-4f9b-995d-059433bc3267";
             let _ = mdm.mqtt_connect(device_id)?;
 
             println!("entering queue receive loop ...");