Final (general) approach, still needs some tweaing and validation though

.gitignore

@@ -1,3 +1,5 @@
+.idea
+
 # Byte-compiled / optimized / DLL files
 __pycache__/
 *.py[cod]

README.md

@@ -1,2 +1,20 @@
 # network-device-offline-monitor
-A simple way of getting notified by email if a "always online" network device goes offline for any reason
+A simple way of getting notified by email if one or more local network devices go offline for any reason.
+
+This will scan any IP ranges specified in config.ini (see `IpRangesToScan`) and checks that any IPs mentioned in `RequiredIps` are online. If they aren't, it will send an email to the specified notification email.
+
+This script is designed for Linux since it uses nmap, however it might be possible to run it on a Windows OS as long as nmap is installed (https://nmap.org/book/inst-windows.html) and available on the `PATH`. I haven't tested this though.
+
+## How To Run
+
+This uses the Mailersend API to send emails (although naturally you can use your own provider or approach by modifying `send_email_notification()`).
+
+The Mailersend API key can only be specified by an environment variable: `MAILERSEND_API_KEY`
+
+So you can run this script by modifying `config.ini` as required, and then running something like:
+
+> MAILERSEND_API_KEY='changeme' python3 main.py
+
+You can also change the logging level by adding a `--loglevel` param, for example by running:
+
+> MAILERSEND_API_KEY='changeme' python3 main.py --loglevel debug

config.ini

@@ -3,9 +3,8 @@ IpRangesToScan =
     192.168.4.0/24
     192.168.6.0/24
     192.168.7.0/24
+OfflineNotificationName = Tristan Perry
 OfflineNotificationEmail = [email protected]
 RequiredIps =
     192.168.7.254
-    192.168.7.0
     192.168.4.27
-Blah = Test

main.py

@@ -2,6 +2,9 @@
 import argparse
 import logging
 import nmap3
+import os
+
+from mailersend import emails
 
 logger = logging.getLogger(__name__)
 
@@ -11,18 +14,19 @@ def to_list(string: str) -> list:
     return list(filter(None, split))
 
 
-def load_config_values() -> tuple[list, str, list]:
+def load_config_values() -> tuple[list, str, str, list]:
     config = configparser.ConfigParser()
     config.read('config.ini')
 
     to_scan = config['DEFAULT']['IpRangesToScan']
+    notification_name = config['DEFAULT']['OfflineNotificationName']
     notification_email = config['DEFAULT']['OfflineNotificationEmail']
     required_ips = config['DEFAULT']['RequiredIps']
     logger.debug('Config loaded. (to_scan) %s, (email) %s, (ips) %s', to_scan, notification_email, required_ips)
 
     # TODO validate
 
-    return to_list(to_scan), notification_email, to_list(required_ips)
+    return to_list(to_scan), notification_name, notification_email, to_list(required_ips)
 
 
 def get_active_local_ips(to_scan: list) -> list:
@@ -36,7 +40,8 @@ def get_active_local_ips(to_scan: list) -> list:
         logger.debug('Results for host range %s', host)
         logger.debug(results)
 
-        up_ips = {ip: result for ip, result in results.items() if 'state' in result and result['state']['state'] == 'up'}
+        up_ips = {ip: result for ip, result in results.items() if
+                  'state' in result and result['state']['state'] == 'up'}
 
         up_ips_list = list(up_ips.keys())
         logger.debug('%s IPs are UP for host range %s', up_ips_list, host)
@@ -45,8 +50,40 @@ def get_active_local_ips(to_scan: list) -> list:
     return active_ips_in_range
 
 
-def send_email_notification(error_ips: list, notification_email: str) -> None:
+def send_email_notification(error_ips: list, notification_name: str, notification_email: str) -> None:
     logger.error('IP(s) %s are offline, sending email to %s', error_ips, notification_email)
+    mailer = emails.NewEmail(os.getenv('MAILERSEND_API_KEY'))
+
+    mail_body = {}
+
+    mail_from = {
+        "name": "Offline Notifier",
+        "email": "[email protected]",
+    }
+
+    recipients = [
+        {
+            "name": notification_name,
+            "email": notification_email,
+        }
+    ]
+
+    reply_to = [
+        {
+            "name": "No Reply",
+            "email": "[email protected]",
+        }
+    ]
+
+    mailer.set_mail_from(mail_from, mail_body)
+    mailer.set_mail_to(recipients, mail_body)
+    mailer.set_reply_to(reply_to, mail_body)
+    mailer.set_subject("Network Device(s) Offline", mail_body)
+    mailer.set_plaintext_content("Warning: the following required IP addresses are offline: " + ', '.join(error_ips),
+                                 mail_body)
+
+    response = mailer.send(mail_body)
+    logger.debug("Email response: %s", response)
 
 
 if __name__ == '__main__':
@@ -59,14 +96,12 @@ def send_email_notification(error_ips: list, notification_email: str) -> None:
     logging.basicConfig(level=args.loglevel.upper())
     logging.info('Logging setup')
 
-    ip_ranges_to_scan, email, required_ips = load_config_values()
+    ip_ranges_to_scan, name, email, required_ips = load_config_values()
     all_active_ips = get_active_local_ips(ip_ranges_to_scan)
     logger.info('All active IPs: %s', all_active_ips)
 
     offline_ips = list(set(required_ips) - set(all_active_ips))
     logger.info('Offline IPs %s', offline_ips)
 
     if offline_ips:
-        send_email_notification(offline_ips)
-
-# See PyCharm help at https://www.jetbrains.com/help/pycharm/
+        send_email_notification(offline_ips, name, email)

requirements.txt

@@ -1,2 +1,3 @@
 configparser~=6.0.1
-python3-nmap~=1.6.0
+python3-nmap~=1.6.0
+mailersend~=0.5.6