Here are the data structures with brief descriptions:

Ccnt_str
Ccoap_address_t	Multi-purpose address abstraction
Ccoap_async_state_t
Ccoap_attr_t
Ccoap_block_t	Structure of Block options
Ccoap_context_t	The CoAP stack's global state is stored in a coap_context_t object
Ccoap_endpoint_t	Abstraction of virtual endpoint that can be attached to coap_context_t
Ccoap_hdr_t
Ccoap_mid_cache_t
Ccoap_opt_iterator_t	Iterator to run through PDU options
Ccoap_option	Structures for more convenient handling of options
Ccoap_option_t	Representation of CoAP options
Ccoap_packet_t
Ccoap_pdu_t	Header structure for CoAP PDUs
Ccoap_queue_t
Ccoap_resource_t
Ccoap_subscription_t	Subscriber information
Ccoap_uri_t	Representation of parsed URI
Cerror_desc_t
Cin6_pktinfo
Cin_pktinfo
Copt_filter
Cstr
CUT_hash_bucket
CUT_hash_handle
CUT_hash_table