diff --git a/sdm630_mqtt.py b/sdm630_mqtt.py
index 0bd413c..244f39c 100644
--- a/sdm630_mqtt.py
+++ b/sdm630_mqtt.py
@@ -31,6 +31,8 @@ class SDM630_MQTT:
         self.mqtt.on_connect = self._on_mqtt_connect
         self.mqtt.on_disconnect = self._on_mqtt_disconnect
 
+        self.idx = 0
+
     def _publish(self, topic, msg):
         LOG.debug(f"_publish({topic!r}, {msg!r})")
         self.mqtt.publish(f"{self.mqtt_prefix.rstrip('/')}/{topic}", msg)
@@ -45,67 +47,71 @@ class SDM630_MQTT:
         LOG.debug("_start()")
         self.mqtt.connect(self.mqtt_host, self.mqtt_port, 10)
         self.mqtt.loop_start()
+        self.modbus.open()
 
     def stop(self):
+        LOG.debug("_stop()")
+        self.modbus.close()
         self.mqtt.loop_stop()
         self.mqtt.disconnect()
 
     def request_and_publish(self):
-        self.modbus.open()
-        for idx, (readable, address) in enumerate(
-            {
-                "active-power/L1": 0x000C,
-                "active-power/L2": 0x000E,
-                "active-power/L3": 0x0010,
-                "active-power/total": 0x0034,
-                "apparent-power/L1": 0x0012,
-                "apparent-power/L2": 0x0014,
-                "apparent-power/L3": 0x0016,
-                "apparent-power/total": 0x0038,
-                "current-demand/L1": 0x0102,
-                "current-demand/L2": 0x0104,
-                "current-demand/L3": 0x0106,
-                "current-demand/N": 0x0068,
-                "current-demand/max_L1": 0x0108,
-                "current-demand/max_L2": 0x010A,
-                "current-demand/max_L3": 0x010C,
-                "current-demand/max_N": 0x006A,
-                "current/L1": 0x0006,
-                "current/L2": 0x0008,
-                "current/L3": 0x000A,
-                "current/average": 0x002E,
-                "current/neutral": 0x00E0,
-                "current/total": 0x0030,
-                "export_kVArh": 0x004C,
-                "export_kWh": 0x004A,
-                "frequency": 0x0046,
-                "import_kVArh": 0x004E,
-                "import_kWh": 0x0048,
-                "phase-angle/L1": 0x0024,
-                "phase-angle/L2": 0x0026,
-                "phase-angle/L3": 0x0028,
-                "phase-angle/total": 0x003E,
-                "power-demand/max": 0x0056,
-                "power-demand/total": 0x0054,
-                "power-factor/L1": 0x001E,
-                "power-factor/L2": 0x0020,
-                "power-factor/L3": 0x0022,
-                "power-factor/total": 0x003E,
-                "reactive-power/L1": 0x0018,
-                "reactive-power/L2": 0x001A,
-                "reactive-power/L3": 0x001E,
-                "reactive-power/total": 0x003C,
-                "voltage/L1_L2": 0x00C8,
-                "voltage/L1_N": 0x0000,
-                "voltage/L2_L3": 0x00CA,
-                "voltage/L2_N": 0x0002,
-                "voltage/L3_L1": 0x00CC,
-                "voltage/L3_N": 0x0004,
-                "voltage/average": 0x002A,
-            }.items()
-        ):
+        for readable, address in {
+            "active-power/L1": 0x000C,
+            "active-power/L2": 0x000E,
+            "active-power/L3": 0x0010,
+            "active-power/total": 0x0034,
+            "apparent-power/L1": 0x0012,
+            "apparent-power/L2": 0x0014,
+            "apparent-power/L3": 0x0016,
+            "apparent-power/total": 0x0038,
+            "current-demand/L1": 0x0102,
+            "current-demand/L2": 0x0104,
+            "current-demand/L3": 0x0106,
+            "current-demand/N": 0x0068,
+            "current-demand/max_L1": 0x0108,
+            "current-demand/max_L2": 0x010A,
+            "current-demand/max_L3": 0x010C,
+            "current-demand/max_N": 0x006A,
+            "current/L1": 0x0006,
+            "current/L2": 0x0008,
+            "current/L3": 0x000A,
+            "current/average": 0x002E,
+            "current/neutral": 0x00E0,
+            "current/total": 0x0030,
+            "export_kVArh": 0x004C,
+            "export_kWh": 0x004A,
+            "frequency": 0x0046,
+            "import_kVArh": 0x004E,
+            "import_kWh": 0x0048,
+            "phase-angle/L1": 0x0024,
+            "phase-angle/L2": 0x0026,
+            "phase-angle/L3": 0x0028,
+            "phase-angle/total": 0x003E,
+            "power-demand/max": 0x0056,
+            "power-demand/total": 0x0054,
+            "power-factor/L1": 0x001E,
+            "power-factor/L2": 0x0020,
+            "power-factor/L3": 0x0022,
+            "power-factor/total": 0x003E,
+            "reactive-power/L1": 0x0018,
+            "reactive-power/L2": 0x001A,
+            "reactive-power/L3": 0x001E,
+            "reactive-power/total": 0x003C,
+            "voltage/L1_L2": 0x00C8,
+            "voltage/L1_N": 0x0000,
+            "voltage/L2_L3": 0x00CA,
+            "voltage/L2_N": 0x0002,
+            "voltage/L3_L1": 0x00CC,
+            "voltage/L3_N": 0x0004,
+            "voltage/average": 0x002A,
+        }.items():
             try:
                 read = self.modbus.read_input_registers(address, 2)
+                self.idx += 1
+                if read is None:
+                    LOG.error(f'reading {readable} was None: {self.modbus.last_error_as_txt}')
+                    continue
                 longs = word_list_to_long(read)
                 if len(longs) == 1:
                     self._publish(readable, decode_ieee(longs[0]))
@@ -113,10 +119,10 @@ class SDM630_MQTT:
                     self._publish(readable, sum([decode_ieee(x) for x in longs]))
             except Exception:
                 LOG.exception(f'error while reading {readable} from meter')
-            if idx % 20:
+            if self.idx >= 20:
                 self.modbus.close()
                 self.modbus.open()
-        self.modbus.close()
+                self.idx = 0
 
 
 if __name__ == "__main__":
@@ -127,11 +133,12 @@ if __name__ == "__main__":
     except Exception as e:
         print(f"Usage: {argv[0]} config.toml")
         exit(1)
-    client = SDM630_MQTT(config)
-    client.start()
     try:
+        client = SDM630_MQTT(config)
+        client.start()
         while True:
             client.request_and_publish()
     except Exception as e:
         LOG.exception("oops")
+    finally:
         client.stop()