---
title: Design Concept
---

Mongoose is a multi-protocol networking library that implements non-blocking,
asyncronous IO and provides event-based API. It has three basic data structures:

- [`struct mg_mgr`](#TODO) is an event manager that holds all active
  connections
- [`struct mg_connection`](#TODO) describes a connection
- [`struct mbuf`](#TODO) describes data buffer (received or sent data)

Connections could be either *listening*, *outbound* or *inbound*.  Outbound
connections are created by [`mg_connect()`](#TODO) call.  Listening connections
are created by [`mg_bind()`](#TODO) call.  Inbound connections are those
accepted by a listening connection.  Each connection is described by [`struct
mg_connection`](#TODO) structure, which has a number of fields like socket,
event handler function, send/receive buffer, flags, et cetera.

Mongoose usage pattern is to declare and initialize event manager, create
connections and create an event loop by calling [`mg_mgr_poll()`](#TODO) in a
loop.  [`mg_mgr_poll()`](#TODO) iterates over all sockets, accepts new
connections, sends and receives data, closes connections, and calls event
handler functions for the respective events.