mongoose/docs/c-api/coap.h/mg_coap_send_ack.md

title	decl_name	symbol_kind	signature
mg_coap_send_ack()	mg_coap_send_ack	func	uint32_t mg_coap_send_ack(struct mg_connection *nc, uint16_t msg_id);

Composes CoAP acknowledgement from mg_coap_message and sends it into nc connection. Return value: see mg_coap_send_message()