diff --git a/net/adc_device_netserver.h b/net/adc_device_netserver.h
index ab8efd5..4c4b031 100644
--- a/net/adc_device_netserver.h
+++ b/net/adc_device_netserver.h
@@ -221,7 +221,8 @@ public:
             : _ident(),
               _netService(std::move(srv)),
               _serverPtr(srv_ptr),
-              _bindDevice(srv_ptr->_devices.size() ? srv_ptr->_devices.begin()->second : AdcDeviceNetServer::nullDevice)
+              _bindDevice(srv_ptr->_devices.size() ? &srv_ptr->_devices.begin()->second
+                                                   : &AdcDeviceNetServer::nullDevice)
         {
             if constexpr (std::is_array_v<std::remove_cvref_t<R>>) {
                 _ident = id;
@@ -274,7 +275,7 @@ public:
         netsession_ident_t _ident;
         netservice_t _netService;
         AdcDeviceNetServer* _serverPtr;
-        AdcDeviceNetServer::DeviceWrapper& _bindDevice;
+        AdcDeviceNetServer::DeviceWrapper* _bindDevice;
 
         std::chrono::duration<size_t> _recvTimeout = std::chrono::seconds(3600);
         std::chrono::duration<size_t> _sendTimeout = std::chrono::seconds(5);
@@ -290,8 +291,6 @@ public:
             auto get_elem = [&attrs](size_t idx) {
                 if (idx < attrs.size()) {
                     return attrs[idx];
-                    // auto& el = attrs[idx];
-                    // return serialized_t(el.begin(), el.end());
                 } else {
                     return serialized_t();
                 }
@@ -307,13 +306,13 @@ public:
                         bool found = false;
                         for (auto& [ptr, dev_wr] : _serverPtr->_devices) {
                             if (std::ranges::equal(dev_wr.ident(), dev_name)) {
-                                _bindDevice = dev_wr;
+                                _bindDevice = &dev_wr;
                                 found = true;
                                 break;
                             }
                         }
                         if (found) {
-                            msg.ack(attrs);
+                            msg.ack(msg_t::DEVICE_KEY, attrs);
                         } else {
                             msg.err(std::make_error_code(AdcDeviceNetServerSessionError::ERROR_UNKNOWN_DEVICE_ID));
                         }
@@ -325,14 +324,14 @@ public:
                     for (auto& [ptr, dev_wr] : _serverPtr->_devices) {
                         names.emplace_back(dev_wr.ident());
                     }
-                    msg.ack(names);
+                    msg.ack(msg_t::NAMES_KEY, names);
                 } else if (msg.isHELLO()) {
+                    msg.ack(msg_t::HELLO_KEY, _serverPtr->_serverIdent);
                 } else if (msg.isGET()) {  // get attribute value
                     attrs = msg.template attrs<attr_vec_t>(0, 1);
                     if (attrs.size()) {
-                        auto val = _bindDevice.getAttr(get_elem(0));
-                        // msg.ack(get_elem(0), serialized_t{val.begin(), val.end()});
-                        msg.ack(get_elem(0), val);
+                        auto val = _bindDevice->getAttr(get_elem(0));
+                        msg.ack(msg_t::GET_KEY, get_elem(0), val);
                     } else {  // no attr name!
                         msg.err(std::make_error_code(AdcDeviceNetServerSessionError::ERROR_NO_PROTO_ATTRNAME));
                     }
@@ -340,9 +339,8 @@ public:
                     attrs = msg.template attrs<attr_vec_t>(0);
                     if (attrs.size() >= 2) {
                         auto val = msg.template joinAttrs<serialized_t>(1);
-                        _bindDevice.setAttr(get_elem(0), val);
-                        // msg.ack(get_elem(0), serialized_t{val.begin(), val.end()});
-                        msg.ack(get_elem(0), val);
+                        _bindDevice->setAttr(get_elem(0), val);
+                        msg.ack(msg_t::SET_KEY, get_elem(0), val);
                     } else {  // no attr name or its value!
                         if (attrs.size() == 1) {
                             msg.err(std::make_error_code(AdcDeviceNetServerSessionError::ERROR_NO_PROTO_ATTRVALUE));
@@ -354,8 +352,8 @@ public:
                     attrs = msg.template attrs<attr_vec_t>(0, 1);
                     if (attrs.size()) {
                         auto cmd_name = get_elem(0);
-                        _bindDevice.exec(cmd_name);
-                        msg.ack(cmd_name);
+                        _bindDevice->exec(cmd_name);
+                        msg.ack(msg_t::CMD_KEY, cmd_name);
                     } else {  // no cmd name!
                         msg.err(std::make_error_code(AdcDeviceNetServerSessionError::ERROR_NO_PROTO_CMDNAME));
                     }