Test this machines network connection.
Two types of tests are performed depending on if the machine has a public IP address present or if it only has a private address (or addresses).
The public IP address test is primarily for when running a server as no tests are needed for clients with public addresses. In order
for the public IP test to succeed a server instance must be started. A test server will try to connect to the
IP and port of the local server and thus it is shown in the server is connectable. If not then a firewall is most likely
blocking the server port. A server instance needs to be running so that the test server has something to connect
to.
The other test is for checking NAT punchthrough capabilities. This is a valid test for both servers and clients
and can be performed without any prior setup. There are 4 types of NAT test results (see ConnectionTesterStatus): __Full Cone_, Address Restricted Cone, Port restricted and
Symmetric.
First two types offer full NAT punchthrough support and can connect to any type. Port restricted type cannot connect to or receive a connection from symmetric
type. Symmetric if worst and cannot connect to other symmetric types or port restricted type. The latter two are labelled
as offering limited NAT punchthrough support.
This function is asynchronous and might not return a valid result right away because the tests needs
some time to complete (1-2 seconds). After test completion the test result is only returned when the function is called again,
a full network test is not redone. That way it is safe to poll the function frequently. If another test is desired,
like if the network connection has been altered, then the forceTest parameter should be passed as true.
The function returns a ConnectionTesterStatus enum.