Wt

Socket operations in asio nearly always have two variants:

1. call(), which will throw an exception
2. call(error_code& ec), which does not throw

In case of operations where we do not really care about the error code, we should consistently pass a reference to the code, so that it can be set, but otherwise safely ignored.
Currently, there are cases where the shutdown is initiated with an ignored_ec, but a further call to cancel() or close() does not use the code, and can potentially throw.

Additional improvement:
There are places where a try/catch is performed. This is fine, as we may want to log output of it. But it ought to be handled consistently.
Either we work with error code, or either we work with exceptions.