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from threading import Thread
import socket
import time
import numpy
import opcua
from opcua import Client
from tango import DevState
class CommClient(Thread):
"""
The ProtocolHandler class is the generic interface class between the tango attribute_wrapper and the outside world
"""
def __init__(self, standby_func, fault_func, streams, try_interval=2):
"""
"""
self.standby_func = standby_func
self.fault_func = fault_func
self.try_interval = try_interval
self.streams = streams
self.stopping = False
self.connected = False
super().__init__(daemon=True)
def connect(self):
"""
Function used to connect to the client.
"""
self.connected = True
return True
def disconnect(self):
"""
Function used to connect to the client.
"""
self.connected = False
def run(self):
# Explicitly connect
if not self.connect():
# hardware or infra is down -- needs fixing first
self.fault_func()
return
self.standby_func()
self.stopping = False
while not self.stopping:
# keep trying to connect
print("connected check")
if not self.connected:
print("not connected, try to connect")
if self.connect():
print("connected now, call on_func")
self.standby_func()
else:
# we retry only once, to catch exotic network issues. if the infra or hardware is down,
# our device cannot help, and must be reinitialised after the infra or hardware is fixed.
self.fault_func()
return
# keep checking if the connection is still alive
try:
while not self.stopping:
self.ping()
time.sleep(self.try_interval)
except Exception as e:
self.streams.error_stream("Fault condition in communication detected.", e)
# technically, we may not have dropped the connection, but encounter a different error. so explicitly disconnect.
self.disconnect()
# signal that we're disconnected
self.fault_func()
def ping(self):
pass
def stop(self):
"""
Stop connecting & disconnect. Can take a few seconds for the timeouts to hit.
"""
if not self.ident:
# have not yet been started, so nothing to do
return
self.stopping = True
self.join()
self.disconnect()
def setup_attribute(self, annotation, attribute):
This function is responsible for providing the attribute_wrapper with a read/write function
How this is done is implementation specific.
The setup-attribute has access to the comms_annotation provided to the attribute wrapper to pass along to the comms client
as well as a reference to the attribute itself.
Examples:
- File system: get_mapping returns functions that read/write a fixed
number of bytes at a fixed location in a file. (SEEK)
- OPC-UA: traverse the OPC-UA tree until the node is found.
Then return the read/write functions for that node which automatically
convert values between Python and OPC-UA.
AssertionError("the setup_attribute must be implemented and provide return a valid read/write function for the attribute")