lwIP 2.2.1 Lightweight IP stack

Modules
Socket API
APIs

## Modules
| Interface Identification API
| NETDB API

## Detailed Description

BSD-style socket API.
Thread-safe, to be called from non-TCPIP threads only.
Can be activated by defining LWIP_SOCKET to 1.
Header is in posix/sys/socket.h
The socket API is a compatibility API for existing applications, currently it is built on top of the sequential API. It is meant to provide all functions needed to run socket API applications running on other platforms (e.g. unix / windows etc.). However, due to limitations in the specification of this API, there might be incompatibilities that require small modifications of existing programs.