Fix getEncryption() issue for multiple client.

This is a workaround for [getEncryption() issue #5](https://github.com/hoaproject/Socket/issues/5)

I know is maybe not the best way, but after lot review I don't find how implement that otherwise.
That can be a good beginning for work on best way.

Best Regards.
named with prefix because should not be called by hand, but must be public for Connection class can call function.
are you ok with that ?