Bachelorarbeit Lukas Friedrichsen 20170802 (final)

Einrichtung_RPI/files/89-mqtt_node_client.rules

+KERNEL=="ttyUSB?", SUBSYSTEM=="tty", ACTION=="add", RUN+="/bin/bash service mqtt_node_client restart"
+KERNEL=="ttyUSB?", SUBSYSTEM=="tty", ACTION=="remove", RUN+="/bin/bash service mqtt_node_client stop"

Einrichtung_RPI/files/hostapd.conf

+########General settings########
+#WiFi interface to use
+interface=wlan0
+#Driver to use (nl80211 most of the time)
+driver=nl80211
+#SSID of the access point
+ssid=EMRA_Prototype_Network
+#WiFi mode (a, b, g or n; setting to g ensures backward compatiblity)
+hw_mode=g
+#WiFi channel to use (1 - 13; even though this depends on the individual surroundings, high (e.g. 13) and low (e.g. 1) channels tend to have less interferences than the mid-range frequencies)
+channel=1
+#Options for mac address filtering
+#0 - Accept all devices except blacklisted ones (as listed in deny_mac_file)
+#1 - Deny all devices except whitelisted ones (as listed in accept_mac_file)
+macaddr_acl=0
+#deny_mac_file=/etc/hostapd/hostapd.deny
+#accept_mac_file=/etc/hostapd/hostapd.accept
+#Options for SSID broadcasting
+#0 - SSID broadcasting activated
+#1 - SSID broadcasting deactivated
+ignore_broadcast_ssid=0
+#Authentication algorithm to use
+#1 - only open system authentication
+#2 - both open system authentication and shared key authentication
+auth_algs=1
+# 
+#####WPA and WPA2 settings#####
+#WPA mode to use
+#1 - WPA only
+#2 - WPA2 only
+#3 - both
+wpa=2
+#WPA passphrase of the access point
+wpa_passphrase=EnergyMeterReadoutAutomation
+#WPA key management
+wpa_key_mgmt=WPA-PSK
+#Security protocol used by WPA
+wpa_pairwise=TKIP
+#Security protocol used by RSN
+rsn_pairwise=CCMP

Einrichtung_RPI/files/interfaces

+# interfaces(5) file used by ifup(8) and ifdown(8)
+
+# Please note that this file is written to be used with dhcpcd
+# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'
+
+# Include files from /etc/network/interfaces.d:
+source-directory /etc/network/interfaces.d
+
+auto lo
+iface lo inet loopback
+
+auto eth0
+allow-hotplug eth0
+iface eth0 inet manual
+
+allow-hotplug wlan0
+iface wlan0 inet static
+    address 192.168.42.1
+    netmask 255.255.255.0
+    network 192.168.42.0
+    broadcast 192.168.42.255
+    gateway 192.168.42.1
+
+allow-hotplug wlan1
+iface wlan1 inet manual
+    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

Einrichtung_RPI/files/mosquitto.conf

+# Place your local configuration in /etc/mosquitto/conf.d/
+#
+# A full description of the configuration file is at
+# /usr/share/doc/mosquitto/examples/mosquitto.conf.example
+
+# Include directory for external configuration-files
+include_dir /etc/mosquitto/conf.d
+
+# Location of the PID (process ID) file; keep in sync with
+# PIDFILE in /etc/init.d/mosquitto
+pid_file /var/run/mosquitto.pid
+
+# System configuration
+store_clean_interval 20
+sys_interval 15
+
+# Logging
+log_dest file /var/log/mosquitto/mosquitto.log
+log_type all 
+log_timestamp true
+connection_messages true
+
+# Persistence   
+persistence true
+persistence_location /var/lib/mosquitto/
+autosave_interval 900
+
+# Listener
+bind_address 192.168.42.1
+port 8883
+
+# User authentication
+allow_anonymous false
+#use_username_as_clientid true
+password_file /etc/mosquitto/usr_auth
+
+# Encryption (SSL/TLS)
+cafile /etc/mosquitto/ca_certificates/ca_cert.pem
+certfile /etc/mosquitto/certs/server_cert.pem
+keyfile /etc/mosquitto/certs/server_key.pem
+require_certificate false

Einrichtung_RPI/files/mqtt_node_client

+#!/bin/sh
+
+### BEGIN INIT INFO
+# Provides:             mqtt_node_client
+# Required-Start:       $remote_fs $syslog $network
+# Required-Stop:        $remote_fs $syslog $network
+# Default-Start:
+# Default-Stop:         0 1 6
+# Short-Description:    MQTT v3.1 client and Modbus RTU/M-Bus master
+# Description:
+#  This combined implementation of the Python paho-mqtt client, pymodbus and
+#  python-mbus provides the functionality to act as a gateway between Modbus RTU
+#  resp. M-Bus devices and an OPC-server via MQTT. The values received from the
+#  connected devices are logged in the CSV format and published on a MQTT broker
+#  over WLAN afterwards.
+### END INIT INFO
+
+# When this option is enabled, the shell immediately exits if any command fails
+set -e
+
+PIDFILE=/var/run/mqtt_node_client.pid
+DAEMON=/usr/local/sbin/mqtt_node_client.py
+
+# Does the file exist and is the permission to execute it granted
+test -x ${DAEMON} || exit 0
+
+# Set all files to be created from here on to -rw-r--r--
+umask 022
+
+# Load init functions
+. /lib/lsb/init-functions
+
+# Start the daemon
+start() {
+  log_daemon_msg "Starting daemon:" "mqtt_server_client"
+  if start-stop-daemon --start --quiet --oknodo --background --make-pidfile --pidfile ${PIDFILE} --startas /bin/bash -- -c "${DAEMON}"; then
+      log_end_msg 0
+  else
+      log_end_msg 1
+  fi
+}
+
+# Stop the daemon
+stop() {
+  log_daemon_msg "Stopping daemon:" "mqtt_server_client"
+  if start-stop-daemon --stop --quiet --oknodo --pidfile ${PIDFILE}; then
+      log_end_msg 0
+      rm -f ${PIDFILE}
+  else
+      log_end_msg 1
+  fi
+}
+
+case "$1" in
+  start)
+        start
+        ;;
+  stop)
+        stop
+        ;;
+
+  restart)
+        stop
+        start
+        ;;
+
+  status)
+        status_of_proc -p ${PIDFILE} ${DAEMON} mqtt_server_client && exit 0 || exit $?
+        ;;
+
+  *)
+        log_action_msg "Usage: /etc/init.d/mqtt_server_client {start|stop|restart|status}"
+        exit 1
+esac
+
+exit 0

Einrichtung_RPI/files/mqtt_server_client

+#!/bin/sh
+
+### BEGIN INIT INFO
+# Provides:             mqtt_server_client
+# Required-Start:       $remote_fs $syslog $network mosquitto
+# Required-Stop:        $remote_fs $syslog $network mosquitto
+# Default-Start:        2 3 4 5
+# Default-Stop:         0 1 6
+# Short-Description:    MQTT v3.1 client
+# Description:
+#  This implementation of the Python paho-mqtt client allows to connect to a
+#  local MQTT broker and log the data published on definable topics. Furthermore,
+#  it provides the functionality to act as an interface towards other, non-MQTT
+#  based applications like e.g. an OPC UA server by generating data-exchange-files
+#  in the CSV format, containing the most current values published on the
+#  subscribed topics at all times.
+### END INIT INFO
+
+# When this option is on, when any command fails, the shell immediately exits
+set -e
+
+PIDFILE=/var/run/mqtt_server_client.pid
+DAEMON=/usr/local/sbin/mqtt_server_client.py
+
+# Does the file exist and is the permission to execute it granted
+test -x ${DAEMON} || exit 0
+
+# Set all files to be created from here on to -rw-r--r--
+umask 022
+
+# Load init functions
+. /lib/lsb/init-functions
+
+# Start the daemon
+start() {
+  log_daemon_msg "Starting daemon:" "mqtt_server_client"
+  if start-stop-daemon --start --quiet --oknodo --background --make-pidfile --pidfile ${PIDFILE} --startas /bin/bash -- -c "${DAEMON}"; then
+      log_end_msg 0
+  else
+      log_end_msg 1
+  fi
+}
+
+# Stop the daemon
+stop() {
+  log_daemon_msg "Stopping daemon:" "mqtt_server_client"
+  if start-stop-daemon --stop --quiet --oknodo --pidfile ${PIDFILE}; then
+      log_end_msg 0
+      rm -f ${PIDFILE}
+  else
+      log_end_msg 1
+  fi
+}
+
+case "$1" in
+  start)
+        start
+        ;;
+  stop)
+        stop
+        ;;
+
+  restart)
+        stop
+        start
+        ;;
+
+  status)
+        status_of_proc -p ${PIDFILE} ${DAEMON} mqtt_server_client && exit 0 || exit $?
+        ;;
+
+  *)
+        log_action_msg "Usage: /etc/init.d/mqtt_server_client {start|stop|restart|status}"
+        exit 1
+esac
+
+exit 0

Einrichtung_RPI/files/mqtt_server_client.py

+#!/usr/bin/python3
+
+# mqtt_server_client.py
+# Copyright 2017 Lukas Friedrichsen
+# License: Apache License Version 2.0
+#
+# 2017-06-01
+#
+# Description: This implementation of the Python paho-mqtt client allows to
+# connect to a MQTT broker and log the data published on definable topics.
+# Furthermore, it provides the functionality to act as an interface towards other,
+# non-MQTT based applications like e.g. an OPC UA server by generating
+# data-exchange-files in the CSV format, containing the most current values
+# published on the subscribed topics at all times.
+
+import paho.mqtt.client as mqtt
+import time
+import ssl
+import sys
+import os
+
+#------------------------------#
+########### Settings ###########
+#------------------------------#
+
+# General:
+
+# System paths
+_LOG='/var/log/mqtt_server_client/mqtt_server_client.log'
+_DB='/var/lib/mqtt_server_client/mqtt_server_client.db.csv'
+_EXCHANGE_DIR='/usr/local/var/'
+
+_USER_CREDENTIALS='/usr/local/etc/mqtt_server_client/user_credentials'
+_CA='/usr/local/share/ca-certificates/ca_cert.pem'
+
+# MQTT:
+
+# User credentials
+with open(_USER_CREDENTIALS, 'r') as user_credentials:
+    _USERNAME=user_credentials.readline().rstrip('\n')
+    _PASSWORD=user_credentials.readline().rstrip('\n')
+
+# Topics to subscribe to
+_TOPICS='emra/+'
+
+# CSV delimiter
+_CSV_DELIMITER=','
+
+# Local IP-address to bind the MQTT client to
+_IP_ADDR_LOCAL='127.0.0.1'
+
+# Remote IP-address of the MQTT broker
+_IP_ADDR_REMOTE='192.168.42.1'
+
+# Port of the MQTT broker
+_MQTT_PORT=8883
+
+# Timeout threshold (in s; maximum period allowed between communications with the
+# broker (if no other messages are exchanged, this controls the rate at which the
+# client pings the broker)
+_MQTT_TIMEOUT=60
+
+#------------------------------#
+######## Implementation ########
+#------------------------------#
+
+class MQTT_Server_Client(object):
+    '''
+    This implementation of the Python paho-mqtt client allows to connect to a
+    MQTT broker and log the data published on definable topics.
+
+    Furthermore, it provides the functionality to act as an interface towards
+    other, non-MQTT based applications like e.g. an OPC UA server by generating
+    data-exchange-files in the CSV format, containing the most current values
+    published on the subscribed topics at all times.
+    '''
+
+    # Initialization method, that is called on the creation of every new client
+    # instance; initialize needed class variables and set the destination of the
+    # log- and data-exchange-files
+    def __init__(self, **kwargs):
+        '''
+        Initialization method, that is called on the creation of every new client
+        instance; initialize needed class variables and set the destination of
+        the log- and data-exchange-files
+
+        Permitted transfer parameters:
+        - log_file      (default: /var/log/mqtt_node_client/mqtt_node_client.log)
+        - database      (default: /var/lib/mqtt_node_client/mqtt_node_client.db.csv)
+        - exchange_dir  (default: /usr/local/var/)
+        - delimiter     (default: ,)
+        '''
+        # Evaluate the transfer parameters
+        self._log = kwargs.get('log_file', '/var/log/mqtt_node_client/mqtt_node_client.log')
+        self._db = kwargs.get('database', '/var/lib/mqtt_node_client/mqtt_node_client.db.csv')
+        self._exchange_dir = kwargs.get('exchange_dir', '/usr/local/var/')
+        self._csv_delimiter = kwargs.get('csv_delimiter', ',')
+
+        # Initialize _client
+        self._client = None
+
+    # General:
+
+    # Get the current date and time and format the output
+    # Format: yyyy-mm-dd hh:mm:ss
+    def get_datetime(self):
+        '''Get the current date and time and format the output'''
+        return time.strftime('%Y-%m-%d %H:%M:%S', time.localtime())
+
+    # MQTT:
+
+    # Callback function, which is called after an attempt to connect to the MQTT
+    # broker; evaluate the connection result and, in case of a successfully
+    # established connection, subscribe the defined topics (reconnection is
+    # managed by the network loop in any other case)
+    def _on_connect_cb(self, client_instance, userdata, flags, return_code):
+        '''Callback function, which is called after an attempt to connect to the MQTT broker'''
+        log_buffer=(self.get_datetime()+'_on_connect_cb: Return code: '+mqtt.connack_string(return_code)+'\n')
+
+        # Connection attempt was successfull
+        if return_code == mqtt.CONNACK_ACCEPTED:
+            log_buffer+=(self.get_datetime()+'_on_connect_cb: Subscribing to the defined topics!\n')
+            # Subscribe to the defined topics; retry every 30 seconds if the
+            # subscription fails
+            try:
+                while (self._client.subscribe(topic=self._topics, qos=1)[0] != mqtt.MQTT_ERR_SUCCESS):
+                    log_buffer+=(self.get_datetime()+'_on_connect_cb: Subscription failed! No connection to the broker! Retrying in 30 seconds!\n')
+                    time.sleep(30)
+                log_buffer+=(self.get_datetime()+'_on_connect_cb: Successfully subscribed to the defined topics!\n')
+            except:
+                log_buffer+=(self.get_datetime()+'_on_connect_cb: Error: '+str(sys.exc_info()[1])+'\n')
+        # Connection attempt wasn't successfull
+        else:
+            log_buffer+=(self.get_datetime()+'_on_connect_cb: Trying again!\n')
+
+        # Write the buffer to the log (the usage of a buffer allows to minimalize
+        # file is opened (and therewith occupied) by the program, thus reducing
+        # the risk of an access conflict)
+        with open(self._log, 'a') as log:
+            log.write(log_buffer)
+
+    # Callback function, which is called after the client disconnected the MQTT
+    # broker; evaluate the connection result and, in case of an intended
+    # disconnect, exit the program (reconnection is managed by the network loop
+    # in any other case)
+    def _on_disconnect_cb(self, client_instance, userdata, return_code):
+        '''Callback function, which is called after the client disconnected the MQTT broker'''
+        log_buffer=(self.get_datetime()+' _on_disconnect_cb: Disconnected from the broker! Return code: '+mqtt.error_string(return_code)+'\n')
+
+        # Exit the program if the disconnect was caused by client.disconnect()
+        if return_code == mqtt.MQTT_ERR_SUCCESS:
+            log_buffer+=(self.get_datetime()+' _on_disconnect_cb: Exiting the program!\n')
+
+            # Exit the program
+            sys.exit()
+        else:
+            log_buffer+=(self.get_datetime()+' _on_disconnect_cb: Trying to reconnect!')
+
+        # Write the buffer to the log (the usage of a buffer allows to minimalize
+        # file is opened (and therewith occupied) by the program, thus reducing
+        # the risk of an access conflict)
+        with open(self._log, 'a') as log:
+            log.write(log_buffer)
+
+    # Callback function, that is called everytime a new message is published on
+    # a topic subscribed by the client; log the message received and write it to
+    # the data-exchange-file
+    def _on_message_cb(self, client_instance, userdata, msg):
+        '''Callback function, that is called everytime a new message is published on a topic subscribed by the client'''
+        log_buffer=(self.get_datetime()+'_on_message_cb: Obtained message '+str(msg.payload).lstrip('b').strip("'")+' on topic '+msg.topic+'\n')
+
+        # Write the message received to the database
+        with open(self._db, 'a') as database:
+            database.write(self.get_datetime()+self._csv_delimiter+msg.topic[msg.topic.rfind('/')+1:]+self._csv_delimiter+str(msg.payload).lstrip('b').strip("'")+'\n')
+
+        try:
+            # Create the respective sub-directories in the data-exchange-directory
+            # if they don't exist yet
+            _exchange_file=self._exchange_dir+msg.topic
+            os.makedirs(_exchange_file[:_exchange_file.rfind('/')], exist_ok=True)
+
+            # Generate a temporary file containing the data received
+            with open(_exchange_file+'.temp', 'w') as data_exchange_file:
+                data_exchange_file.write(str(msg.payload).lstrip('b').strip("'"))
+                data_exchange_file.flush()
+                os.fsync(data_exchange_file.fileno())
+        except FileNotFoundError:
+            # Every then and now, the system cleans up the data-exchange-directory
+            # and removes outdate files and empty directories. If this garbage
+            # collector checks on a directory just between os.makedirs(...) and
+            # open(...), it will only see an empty directory and remove it (a
+            # wild runtime-condition occurs). The result is a FileNotFoundError.
+            # In this case, the message received can still be found in the
+            # database, but the respective data-exchange-file isn't created.
+            log_buffer+=(self.get_datetime()+'_on_message_cb: Error! No such file or directory: '+_exchange_file+'\n')
+        except:
+            log_buffer+=(self.get_datetime()+'_on_message_cb: Error: '+str(sys.exc_info()[1])+'\n')
+
+        # Replace the current data-exchange-file with the temporary file
+        #
+        # The OPC UA-server constantly tries to read the content from the data-
+        # exchange-file. So, to avoid complications arising from a simultaneous
+        # access to the resource, the file has to be edited in an atomic manner
+        # ("to make the object thread-safe").
+        # The only real way to achieve this is to write the message to a second
+        # file and replace the original data-exchange-file by it in one step (by
+        # editing the object's inode). This is done via the os.rename(...) command.
+        # According to https://docs.python.org/3/library/os.html:
+        #
+        #       "If successful, the renaming will be an atomic operation (this is
+        #       a POSIX requirement)."
+        try:
+            os.rename(self._exchange_dir+msg.topic+'.temp', self._exchange_dir+msg.topic)
+        except:
+            log_buffer+=(self.get_datetime()+'_on_message_cb: Error: '+str(sys.exc_info()[1])+'\n')
+
+        # Write the buffer to the log (the usage of a buffer allows to minimalize
+        # file is opened (and therewith occupied) by the program, thus reducing
+        # the risk of an access conflict)
+        with open(self._log, 'a') as log:
+            log.write(log_buffer)
+
+    # Initialize and configure the MQTT client
+    def mqtt_node_client_init(self, remote_ip, port, topics, local_ip, username, password, **kwargs):
+        '''
+        Initialize and configure the MQTT client
+
+        Permitted transfer parameters:
+        - client_id (default: value of username)
+        - ca        (default: None)
+        - timeout   (default: 60)
+        '''
+        # Evaluate the transfer parameters
+        cl_id = kwargs.get('client_id', username)
+        ca = kwargs.get('ca', None)
+        timeout = kwargs.get('timeout', 60)
+
+        self._topics = topics
+
+        with open(self._log, 'a') as log:
+            log.write(
+                self.get_datetime()+' mqtt_node_client_init: Initializing and configuring the MQTT client!\n'+
+                self.get_datetime()+' mqtt_node_client_init: Local IP: '+local_ip+'   Remote IP: '+remote_ip+'   Port: '+str(port)+'\n'
+            )
+
+        try:
+            # Initialize the MQTT client and set the respective callback functions
+            self._client = mqtt.Client(client_id=cl_id, clean_session=False, userdata=None, protocol=mqtt.MQTTv31, transport='tcp')
+            self._client.on_connect = self._on_connect_cb
+            self._client.on_disconnect = self._on_disconnect_cb
+            self._client.on_message = self._on_message_cb
+
+            if ca != None:
+                # Configure the encryption related settings like which TLS version
+                # to use when communicating with the broker or where to find the
+                # corresponding CA-certificate
+                self._client.tls_set(ca_certs=ca, certfile=None, keyfile=None, cert_reqs=ssl.CERT_REQUIRED, tls_version=ssl.PROTOCOL_TLSv1_2, ciphers=None)
+
+            # Set username and password
+            self._client.username_pw_set(username=username, password=password)
+
+            # Try to connect to the broker in a non-blocking way and start a
+            # loop to keep the connection alive afterwards. This network loop also
+            # automatically handles the reconnection to the broker in case the
+            # connection is lost without explicitly calling client.disconnect().
+            self._client.connect_async(host=remote_ip, port=port, keepalive=timeout, bind_address=local_ip)
+            self._client.loop_forever(retry_first_connection=True)
+        except:
+            # Log occuring errors
+            with open(self._log, 'a') as log:
+                log.write(self.get_datetime()+' mqtt_node_client_init: Error: '+str(sys.exc_info()[1])+'\n')
+
+            # Check, if the MQTT client has already been initialized
+            if self._client != None:
+                # Disconnect from the MQTT broker
+                self._client.disconnect()
+            else:
+                # Exit the program directly (instead of from _on_disconnect_cb(...))
+                sys.exit()
+
+#------------------------------#
+######### Main program #########
+#------------------------------#
+
+# Create a new instance of MQTT_Node_Client
+client = MQTT_Server_Client(log_file=_LOG, database=_DB, exchange_dir=_EXCHANGE_DIR, csv_delimiter=_CSV_DELIMITER)
+
+# Initialize the MQTT-client
+client.mqtt_node_client_init(remote_ip=_IP_ADDR_REMOTE, port=_MQTT_PORT, topics=_TOPICS, local_ip=_IP_ADDR_LOCAL, username=_USERNAME, password=_PASSWORD, ca=_CA, timeout=_MQTT_TIMEOUT)

Einrichtung_RPI/opc_server/rpi_OPCServer.txt

+(* rpi_OPCServer.project
+ * Copyright 2017 Lukas Friedrichsen
+ * License: Apache License Version 2.0
+ *
+ * 2017-06-08
+ *
+ * Description: CODESYS implementation of a basic OPC UA server for the Raspberry
+ * Pi; serves as the communication interface towards higher level networks
+ *)
+
+PROGRAM PLC_PRG
+VAR CONSTANT
+		(* Defines *)
+		MAX_NODE_COUNT:		UINT:=10;
+END_VAR
+VAR
+		(* Process parameters *)
+        running:       		BOOL:=FALSE;
+        state:		 	    UINT:=0;
+		node_count:			UINT:=0;
+
+		(* Functions *)
+		file_op:            FILE.Open;
+        file_rd:            FILE.Read;
+        file_cl:            FILE.Close;
+
+		(* Files *)
+		handle_file:        CAA.HANDLE;
+		name_file1:         CAA.FILENAME:= '/usr/local/var/emra/rpi_Node1';
+		name_file2:         CAA.FILENAME:= '/usr/local/var/emra/rpi_Node2';
+		name_file3:         CAA.FILENAME:= '/usr/local/var/emra/rpi_Node3';
+		name_file4:         CAA.FILENAME:= '/usr/local/var/emra/rpi_Node4';
+		name_file5:         CAA.FILENAME:= '/usr/local/var/emra/rpi_Node5';
+		name_file6:         CAA.FILENAME:= '/usr/local/var/emra/rpi_Node6';
+		name_file7:         CAA.FILENAME:= '/usr/local/var/emra/rpi_Node7';
+		name_file8:         CAA.FILENAME:= '/usr/local/var/emra/rpi_Node8';
+		name_file9:         CAA.FILENAME:= '/usr/local/var/emra/rpi_Node9';
+		name_file10:        CAA.FILENAME:= '/usr/local/var/emra/rpi_Node10';
+
+		(* Variables *)
+		handle_var_ptr:		POINTER TO STRING:=NULL;
+        opc_node1:	        STRING(64):='';
+		opc_node2:			STRING(64):='';
+		opc_node3:	        STRING(64):='';
+		opc_node4:			STRING(64):='';
+		opc_node5:	        STRING(64):='';
+		opc_node6:			STRING(64):='';
+		opc_node7:	        STRING(64):='';
+		opc_node8:			STRING(64):='';
+		opc_node9:	        STRING(64):='';
+		opc_node10:			STRING(64):='';
+END_VAR
+
+________________________________________________________________________________
+
+(* Main program *)
+IF NOT running THEN
+	(* (Re-)Initialize functions and process parameters *)
+    file_op(xExecute:=FALSE);
+    file_cl(xExecute:=FALSE);
+    file_rd(xExecute:=FALSE);
+	state:=0;
+    running:=TRUE;
+
+	(* Increment node_count until the last file has been reached; begin anew in this case *)
+    node_count:=node_count+1;
+	IF node_count<1 OR node_count>MAX_NODE_COUNT THEN
+		node_count:=1;
+	END_IF
+ELSE
+    CASE state OF
+        0:(* Open file *)
+           	CASE node_count OF
+				(* Choose the file to open as well as the respective variable to write to based on node_count *)
+				1:
+					file_op.sFileName:=name_file1;
+					handle_var_ptr:=ADR(opc_node1);
+				2:
+					file_op.sFileName:=name_file2;
+					handle_var_ptr:=ADR(opc_node2);
+				3:
+					file_op.sFileName:=name_file3;
+					handle_var_ptr:=ADR(opc_node3);
+				4:
+					file_op.sFileName:=name_file4;
+					handle_var_ptr:=ADR(opc_node4);
+				5:
+					file_op.sFileName:=name_file5;
+					handle_var_ptr:=ADR(opc_node5);
+				6:
+					file_op.sFileName:=name_file6;
+					handle_var_ptr:=ADR(opc_node6);
+				7:
+					file_op.sFileName:=name_file7;
+					handle_var_ptr:=ADR(opc_node7);
+				8:
+					file_op.sFileName:=name_file8;
+					handle_var_ptr:=ADR(opc_node8);
+				9:
+					file_op.sFileName:=name_file9;
+					handle_var_ptr:=ADR(opc_node9);
+				10:
+					file_op.sFileName:=name_file10;
+					handle_var_ptr:=ADR(opc_node10);
+			END_CASE
+            file_op.eFileMode:=FILE.MODE.MREAD;
+            file_op.xExclusive:=TRUE;
+            file_op(xExecute:=TRUE);
+            IF file_op.xDone THEN
+                handle_file:=file_op.hFile;
+                state:=1;
+            END_IF
+            IF file_op.xError THEN
+				(* Set the respective variable's value to -1 if the file couldn't be opened *)
+				handle_var_ptr^:='-1';
+				running:=FALSE;
+            END_IF
+
+        1:(* Read file *)
+            file_rd.hFile:=handle_file;
+            file_rd.udiTimeOut:=100000;		(* 100ms Timeout *)
+			file_rd.pBuffer:=handle_var_ptr;
+			file_rd.szBuffer:=SIZEOF(STRING(64));
+            file_rd(xExecute:=TRUE);
+            IF file_rd.xDone THEN
+            	state:=2;
+            END_IF
+            IF file_rd.xError THEN
+                (* Set the respective variable's value to -1 if the file couldn't be read *)
+				handle_var_ptr^:='-1';
+				(* Don't set running to FALSE here since the file has to be closed again!*)
+            END_IF
+
+        2:(* Close file *)
+            file_cl.hFile:=handle_file;
+            file_cl(xExecute:=TRUE);
+            IF file_cl.xDone THEN
+                state:=3;
+            END_IF
+
+        3:(* Re-initialize the process variables and functions and increment node_count *)
+			running:=FALSE;
+    END_CASE
+END_IF

Einrichtung_RPI/scripts/cert_gen.sh

+#!/bin/bash
+# Subject
+SUBJ_BASE="/O=KRONPRINZ GmbH/OU=Innovation Management/emailAddress=lukas.friedrichsen@kronprinz.de"
+SUBJ_CA="/CN=EMRA_MQTT_CA_certificate$SUBJ_BASE"
+SUBJ_SERVER="/CN=EMRA_MQTT_server_certificate$SUBJ_BASE"
+
+# Generate a temporary file to store the x509_v3 extensions for the server-certificate in since they can't be passed directly via the command line
+EXT_TEMP=$(mktemp /tmp/ext_temp.XXX) || { echo "Can't create temporary file!"; exit 1; }
+sed -e 's/^.*&&& //' > $EXT_TEMP << EndExtensions
+	&&& [ Extensions ]
+	&&& basicConstraints=critical,CA:false
+	&&& keyUsage=keyEncipherment
+  &&& extendedKeyUsage=serverAuth
+	&&& subjectAltName=IP:192.168.42.1,IP:127.0.0.1
+EndExtensions
+
+# Remove possible old certificates
+echo "Removing possible old certificates!"
+sudo rm -f /etc/mosquitto/ca_certificates/ca_*
+sudo rm -f /etc/mosquitto/certs/server_*
+
+# CA-certificate
+echo "Generating CA-certificate!"
+sudo openssl req -x509 -sha256 -newkey rsa:2048 -nodes -keyout /etc/mosquitto/ca_certificates/ca_key.pem -days 3652 -extensions v3_ca -subj "$SUBJ_CA" -out /etc/mosquitto/ca_certificates/ca_cert.pem
+sudo chmod 400 /etc/mosquitto/ca_certificates/ca_key.pem
+sudo chmod 444 /etc/mosquitto/ca_certificates/ca_cert.pem
+
+# Server-certificate CSR
+echo "Generating server-certificate CSR!"
+sudo openssl req -sha256 -newkey rsa:2048 -nodes -keyout /etc/mosquitto/certs/server_key.pem -extensions v3_ca -subj "$SUBJ_SERVER" -out /etc/mosquitto/certs/server_cert.csr
+sudo chmod 400 /etc/mosquitto/certs/server_key.pem
+sudo chown mosquitto /etc/mosquitto/certs/server_key.pem
+
+# Sign server-certificate CSR
+echo "Signing server-certificate CSR with the generated CA-certificate!"
+sudo openssl x509 -req -in /etc/mosquitto/certs/server_cert.csr -CA /etc/mosquitto/ca_certificates/ca_cert.pem -CAkey /etc/mosquitto/ca_certificates/ca_key.pem -CAcreateserial -days 3652 -extfile $EXT_TEMP -extensions Extensions -out /etc/mosquitto/certs/server_cert.pem
+sudo chmod 444 /etc/mosquitto/certs/server_cert.pem
+sudo chown mosquitto /etc/mosquitto/certs/server_cert.pem
+
+# Clean up
+sudo rm -f /etc/mosquitto/certs/server_cert.csr
+rm $EXT_TEMP