diff --git a/src/modem.rs b/src/modem.rs
index 9d1e46e..93ff631 100644
--- a/src/modem.rs
+++ b/src/modem.rs
@@ -155,9 +155,8 @@ impl<UART: serial::Uart> Modem<UART> {
 
     pub fn gprs_connect(&mut self)-> Result<()> {
         println!("open gprs ...");
-        let _ = self.send_command(Command::gprs_bearer_open())?;
-
-        Ok(())
+        self.send_command(Command::gprs_bearer_open())
+            .map(|_| ())
     }
 
     pub fn is_gprs_attached(&mut self)-> Result<bool> {
@@ -171,33 +170,33 @@ impl<UART: serial::Uart> Modem<UART> {
     }
 
     pub fn tcp_ssl_disable(&mut self) -> Result<()> {
-        let _ = self.send_command(Command::tcp_ssl_set(false))?;
-        Ok(())
+        self.send_command(Command::tcp_ssl_set(false))
+            .map(|_| ())
     }
 
     pub fn tcp_ssl_enable(&mut self) -> Result<()> {
-        let _ = self.send_command(Command::tcp_ssl_set(true))?;
-        Ok(())
+        self.send_command(Command::tcp_ssl_set(true))
+            .map(|_| ())
     }
 
     pub fn tcp_connect(&mut self, addr: &str, port: u16) -> Result<()> {
-        self.send_command(Command::tcp_connect(addr, port))?;
-        Ok(())
+        self.send_command(Command::tcp_connect(addr, port))
+            .map(|_| ())
     }
 
     pub fn tcp_set_quick_mode(&mut self, mode: bool) -> Result<()> {
-        self.send_command(Command::tcp_set_quick_mode(mode))?;
-        Ok(())
+        self.send_command(Command::tcp_set_quick_mode(mode))
+            .map(|_| ())
     }
 
     pub fn tcp_set_manual_receive(&mut self, is_manual: bool) -> Result<()> {
-        self.send_command(Command::tcp_set_manual_receive(is_manual))?;
-        Ok(())
+        self.send_command(Command::tcp_set_manual_receive(is_manual))
+            .map(|_| ())
     }
 
     pub fn tcp_send(&mut self, buf: &[u8]) -> Result<()> {
-        self.tcp_send_data(buf)?;
-        Ok(())
+        self.tcp_send_data(buf)
+            .map(|_| ())
     }
 
     fn tcp_parse_response_size(&mut self, reply_line: &str) -> Result<usize> {
@@ -271,8 +270,8 @@ impl<UART: serial::Uart> Modem<UART> {
     }
 
     pub fn http_close(&mut self) -> Result<()> {
-        let _ = self.send_command(Command::http_close())?;
-        Ok(())
+        self.send_command(Command::http_close())
+            .map(|_| ())
     }
 
     pub fn chip_info(&mut self) -> Result<()> {
@@ -285,13 +284,13 @@ impl<UART: serial::Uart> Modem<UART> {
     }
 
     pub fn location(&mut self) -> Result<()> {
-        let _ = self.send_command(Command::get_location())?;
-        Ok(())
+        self.send_command(Command::get_location())
+            .map(|_| ())
     }
 
     pub fn ssl_opt(&mut self) -> Result<()> {
-        let _ = self.send_command(Command::ssl_opt())?;
-        Ok(())
+        self.send_command(Command::ssl_opt())
+            .map(|_| ())
     }
 
     fn file_write(&mut self, buf: &[u8], path: &str, append: bool, input_time_sec: usize) -> Result<()> {
@@ -322,23 +321,23 @@ impl<UART: serial::Uart> Modem<UART> {
     }
 
     pub fn fs_list(&mut self, path: &str) -> Result<()> {
-        let _ = self.send_command(Command::fs_list(path))?;
-        Ok(())
+        self.send_command(Command::fs_list(path))
+            .map(|_| ())
     }
 
     pub fn fs_free_space(&mut self) -> Result<()> {
-        let _ = self.send_command(Command::fs_free_size())?;
-        Ok(())
+        self.send_command(Command::fs_free_size())
+            .map(|_| ())
     }
 
     pub fn ssl_set_client_cert(&mut self, path: &str, password: &str) -> Result<()> {
-        let _ = self.send_command(Command::ssl_set_client_cert(path, password))?;
-        Ok(())
+        self.send_command(Command::ssl_set_client_cert(path, password))
+            .map(|_| ())
     }
 
     pub fn ssl_set_root_cert(&mut self, path: &str, filesize: usize) -> Result<()> {
-        let _ = self.send_command(Command::ssl_set_root_cert(path, filesize))?;
-        Ok(())
+        self.send_command(Command::ssl_set_root_cert(path, filesize))
+            .map(|_| ())
     }
 
     fn mqtt_receive_reply(&mut self)  -> std::result::Result<(), anyhow::Error> {