diff --git a/cpp/a.out b/cpp/a.out
index c69e1f3..52c5bcd 100755
Binary files a/cpp/a.out and b/cpp/a.out differ
diff --git a/cpp/main.cpp b/cpp/main.cpp
index f32fc57..c332876 100644
--- a/cpp/main.cpp
+++ b/cpp/main.cpp
@@ -17,17 +17,16 @@ using namespace iflytop;
 class Uart g_uart;
 
 int main(int argc, char *argv[]) {
-  pthread_t       pid1, pid2;
-  pthread_attr_t *pthread_arr1, *pthread_arr2;
-  pthread_arr1 = NULL;
-  pthread_arr2 = NULL;
+  int  rec_len;
+  char buffer[128];
 
   g_uart.open(argv[1]);
 
-  char buffer[128];
-
   while (1) {
-    g_uart.receive(buffer, sizeof(buffer));
+    rec_len = g_uart.receive(buffer, sizeof(buffer));
+    if (rec_len > 0) {
+      g_uart.send(buffer, rec_len);
+    }
     usleep(1000);
   }
   return 0;
diff --git a/cpp/uart.cpp b/cpp/uart.cpp
index 8007cb7..eadbdfb 100644
--- a/cpp/uart.cpp
+++ b/cpp/uart.cpp
@@ -68,8 +68,6 @@ int Uart::send(char *data, int size) {
   sent     = write(m_fd, data, size);
   if (sent > 0) {
     printf("send success, data is  %s\r\n", data);
-  } else {
-    printf("send error!\r\n");
   }
   return sent;
 }
@@ -79,7 +77,6 @@ int Uart::receive(char *data, int size_max) {
   received     = read(m_fd, data, size_max);
   if (received > 0) {
     printf("recv success,recv size is %d,data is  %s\r\n", received, data);
-    Uart::send(data, received);
   }
   return received;
 }