diff --git a/mbus/mbus-protocol.c b/mbus/mbus-protocol.c
index 0e97e30..0fef9c0 100644
--- a/mbus/mbus-protocol.c
+++ b/mbus/mbus-protocol.c
@@ -25,6 +25,30 @@ static char error_str[512];
 //------------------------------------------------------------------------------
 static mbus_slave_data slave_data[MBUS_MAX_PRIMARY_SLAVES];
 
+//
+// init event callback
+//
+void (*_mbus_recv_event)(u_char src_type) = NULL;
+void (*_mbus_send_event)(u_char src_type) = NULL;
+
+//------------------------------------------------------------------------------
+/// Register a function for receive events.
+//------------------------------------------------------------------------------
+void
+mbus_register_recv_event(void (*event)(u_char src_type))
+{
+    _mbus_recv_event = event;
+}
+
+//------------------------------------------------------------------------------
+/// Register a function for send events.
+//------------------------------------------------------------------------------
+void
+mbus_register_send_event(void (*event)(u_char src_type))
+{
+    _mbus_send_event = event;
+}
+
 //------------------------------------------------------------------------------
 /// Return a string that contains an the latest error message.
 //------------------------------------------------------------------------------
diff --git a/mbus/mbus-protocol.h b/mbus/mbus-protocol.h
index cb5cbd1..2c9cc50 100644
--- a/mbus/mbus-protocol.h
+++ b/mbus/mbus-protocol.h
@@ -99,6 +99,12 @@ typedef struct _mbus_slave_data {
 
 #define NITEMS(x) (sizeof(x)/sizeof(x[0]))
 
+//
+// Supported handle types
+//
+#define MBUS_HANDLE_TYPE_TCP    0
+#define MBUS_HANDLE_TYPE_SERIAL 1
+
 //------------------------------------------------------------------------------
 // MBUS FRAME DATA FORMATS
 //
@@ -453,6 +459,17 @@ typedef struct _mbus_data_secondary_address {
 #define MBUS_VARIABLE_DATA_MEDIUM_PRESSURE      0x18
 #define MBUS_VARIABLE_DATA_MEDIUM_ADC           0x19
 
+//
+// Event callback functions
+//
+extern void (*_mbus_recv_event)(u_char src_type);
+extern void (*_mbus_send_event)(u_char src_type);
+
+//
+// Event register functions
+//
+void mbus_register_recv_event(void (*event)(u_char src_type));
+void mbus_register_send_event(void (*event)(u_char src_type));
 
 //
 // variable length records
diff --git a/mbus/mbus-serial.c b/mbus/mbus-serial.c
index 8534bb5..22c5d8c 100644
--- a/mbus/mbus-serial.c
+++ b/mbus/mbus-serial.c
@@ -167,7 +167,15 @@ mbus_serial_send_frame(mbus_serial_handle *handle, mbus_frame *frame)
         return -1;
     }
 
-    if ((ret = write(handle->fd, buff, len)) != len)
+    if ((ret = write(handle->fd, buff, len)) == len)
+    {
+        //
+        // call the send event function, if the callback function is registered
+        // 
+        if (_mbus_send_event)
+                _mbus_send_event(MBUS_HANDLE_TYPE_SERIAL);
+    }
+    else
     {   
         fprintf(stderr, "%s: Failed to write frame to socket (ret = %d: %s)\n", __PRETTY_FUNCTION__, ret, strerror(errno));
         return -1;
@@ -196,7 +204,17 @@ mbus_serial_recv_frame(mbus_serial_handle *handle, mbus_frame *frame)
     do {
         //printf("%s: Attempt to read %d bytes [len = %d]\n", __PRETTY_FUNCTION__, remaining, len);
 
-        if ((nread = read(handle->fd, &buff[len], remaining)) == -1)
+        nread = read(handle->fd, &buff[len], remaining);
+
+        if (nread > 0)
+        {
+            //
+            // call the receive event function, if the callback function is registered
+            // 
+            if (_mbus_recv_event)
+                _mbus_recv_event(MBUS_HANDLE_TYPE_SERIAL);
+        }
+        else if (nread == -1)
         {
        //     fprintf(stderr, "%s: aborting recv frame (remaining = %d, len = %d, nread = %d)\n",
          //          __PRETTY_FUNCTION__, remaining, len, nread);
diff --git a/mbus/mbus-tcp.c b/mbus/mbus-tcp.c
index 33ad5f7..62d21e2 100644
--- a/mbus/mbus-tcp.c
+++ b/mbus/mbus-tcp.c
@@ -138,7 +138,15 @@ mbus_tcp_send_frame(mbus_tcp_handle *handle, mbus_frame *frame)
         return -1;
     }
 
-    if ((ret = write(handle->sock, buff, len)) != len)
+    if ((ret = write(handle->sock, buff, len)) == len)
+    {
+        //
+        // call the send event function, if the callback function is registered
+        // 
+        if (_mbus_send_event)
+                _mbus_send_event(MBUS_HANDLE_TYPE_TCP);
+    }
+    else
     {   
         char error_str[128];
         snprintf(error_str, sizeof(error_str), "%s: Failed to write frame to socket (ret = %d)\n", __PRETTY_FUNCTION__, ret);
@@ -167,8 +175,18 @@ mbus_tcp_recv_frame(mbus_tcp_handle *handle, mbus_frame *frame)
     len = 0;
 
     do {
+    
+        nread = read(handle->sock, &buff[len], remaining);
 
-        if ((nread = read(handle->sock, &buff[len], remaining)) == -1)
+        if (nread > 0)
+        {
+            //
+            // call the receive event function, if the callback function is registered
+            // 
+            if (_mbus_recv_event)
+                _mbus_recv_event(MBUS_HANDLE_TYPE_TCP);
+        }
+        else if (nread == -1)
         {
             mbus_error_str_set("M-Bus tcp transport layer failed to read data.");
             return -1;