mongoose/docs/design-concept/memory-buffers.md

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Memory buffers

Each connection has send and receive buffer, struct mg_connection::send_mbuf and struct mg_connection::recv_mbuf respectively. When data arrives, Mongoose appends received data to the recv_mbuf and triggers MG_EV_RECV event. User may send data back by calling one of the output functions, like mg_send() or mg_printf(). Output functions append data to the send_mbuf. When Mongoose successfully writes data to the socket, it discards data from struct mg_connection::send_mbuf and sends MG_EV_SEND event. When connection is closed, MG_EV_CLOSE event is sent.