TCP sockets never close

[ToveRumar]

When a socket is remotely or locally disconneted it is not closed properly.
In the posix socket framework to need to explicitly close a socket for the resources to be freed and to be able to open new sockets in its place.

A part of this is also that we do not handle errors when sending data, any error is interpreted as a disconnect and the socket descriptor is set to -1. This means we can no longer send or receive anything on this socket since we lost the descriptor. All data traffic would be stopped. This could be an ok handling, if the socket was closed after but since it is not, this is an issue.

[gemenerik]

Fixed in #25