S allius/issue102 (#110)

* hotfix: don't send two MODBUS commands together

* fix unit tests

* remove read loop

* optional sleep between msg read and sending rsp

* wait after read 0.5s before sending a response

* add pending state

* fix state definitions

* determine the connection timeout by the conn state

* avoid sending MODBUS cmds in the inverter's reporting phase

* update changelog

app/src/messages.py

@@ -61,7 +61,9 @@ class State(Enum):
     '''at least one packet received'''
     up = 2
     '''at least one cmd-rsp transaction'''
-    closed = 3
+    pend = 3
+    '''inverter transaction pending, don't send MODBUS cmds'''
+    closed = 4
     '''connection closed'''