Reachability

Reachability is a Python 3 package which allows you to monitor and observe online reachability, and react to these status changes as necessary.

This is done by periodically pinging the Cloudflare DNS IP (1.1.1.1). Reachability is customisable, so you can change the interval and host to ping as necessary.

Installation

You can install Reachability from PyPI

pip install reachability

How to use

To start with, we can easily check the current status from an instance of the reachability class:

from reachability import Reachability

reachability = Reachability()
print(reachability.isonline())

The above show True if connected to the internet, or False if not.

To set up Reachability, instead you can use:

reachability = Reachability(host='8.8.4.4', port=53, timeout=3, status_check_interval=4)

The above will instead ping 8.8.4.4 (Google's DNS Service), on port 53 with a timeout of 3 seconds. status_check_interval is used in more advanced use cases to monitor any status changes as shown below.

Observing changes

Functions and Lambdas

reachability.attach_func(lambda x: print(x))
reachability.start_notify()

This will print True or False on each status change. If for example, we are initially connected to the internet, True will be printed. If the Internet connection is then interrupted, the lambda will be executed again this time printing False.

This will continue until

reachability.stop_notify()

is called. Note however that the lambda will still be attached. To detach it, we must call

reachability.detach_func(x)

where x is a reference to the lambda or function.

Obviously, you can also use something like

def f(isonline):
    if isonline:
        print("FunctionA: We are online")
    else:
        print("FunctionA: We are offline")
    
reachability.attach_func(f)

Observers

Another option is to use an Observer Class as demonstrated below:

from reachability import ReachabilityObserver, Reachability


class ObserverA(ReachabilityObserver):
    def reachability_update(self, isonline: bool) -> None:
        if isonline:
            print("ObserverA: We are online")
        else:
            print("ObserverA: We are offline")
    
reachability = Reachability()
observer_a = ObserverA()
reachability.attach(observer_a)
reachability.start_notify()

ReachabiltyObserver is a simple interface. Classes which use it will implement

def reachability_update(self, is_online: bool) -> None

This method will then be called on Online Reachability changes.

You can have multiple observers attached to a reachability instance. To detach them, simply call