Here are the data structures with brief descriptions:

Ccnt_str
Ccoap_addr_hash_t	Only used for servers for hashing incoming packets
Ccoap_addr_info_t	Resolved addresses information
Ccoap_addr_tuple_t
Ccoap_address_t	Multi-purpose address abstraction
Ccoap_attr_t	Limits the number of subscribers for each resource that this server support
Ccoap_bin_const_t	CoAP binary data definition with const data
Ccoap_binary_t	CoAP binary data definition
Ccoap_block_b_t	Structure of Block options with BERT support
Ccoap_block_t	Structure of Block options
Ccoap_cache_entry_t
Ccoap_cache_key_t
Ccoap_const_char_ptr_t	CoAP union for handling signed / unsigned chars
Ccoap_context_t	The CoAP stack's global state is stored in a coap_context_t object
Ccoap_crypto_aes_ccm_t	The structure that holds the AES Crypto information
Ccoap_crypto_param_t	The common structure that holds the Crypto information
Ccoap_digest_t
Ccoap_dtls_cpsk_info_t	The structure that holds the Client PSK information
Ccoap_dtls_cpsk_t	The structure used for defining the Client PSK setup data to be used
Ccoap_dtls_key_t	The structure that holds the PKI key information
Ccoap_dtls_pki_t	The structure used for defining the PKI setup data to be used
Ccoap_dtls_spsk_info_t	The structure that holds the Server Pre-Shared Key and Identity Hint information
Ccoap_dtls_spsk_t	The structure used for defining the Server PSK setup data to be used
Ccoap_endpoint_t	Abstraction of virtual endpoint that can be attached to coap_context_t
Ccoap_fixed_point_t	Abstraction of a fixed point number that can be used where necessary instead of a float
Ccoap_l_block1_t	Structure to keep track of block1 specific information (Requests)
Ccoap_l_block2_t	Structure to keep track of block2 specific information (Responses)
Ccoap_layer_func_t
Ccoap_lg_crcv_t	Structure to hold large body (many blocks) client receive information
Ccoap_lg_range
Ccoap_lg_srcv_t	Structure to hold large body (many blocks) server receive information
Ccoap_lg_xmit_t	Structure to hold large body (many blocks) transmission information
Ccoap_opt_filter_t
Ccoap_opt_iterator_t	Iterator to run through PDU options
Ccoap_option
Ccoap_option_t	Representation of CoAP options
Ccoap_optlist_t	Representation of chained list of CoAP options to install
Ccoap_oscore_conf_t	The structure used to hold the OSCORE configuration information
Ccoap_packet_t
Ccoap_pdu_t	Structure for CoAP PDUs
Ccoap_pki_key_asn1_t	The structure that holds the PKI ASN.1 (DER) definitions
Ccoap_pki_key_define_t	The structure that holds the PKI Definable key type definitions
Ccoap_pki_key_pem_buf_t	The structure that holds the PKI PEM buffer definitions
Ccoap_pki_key_pem_t	The structure that holds the PKI PEM definitions
Ccoap_pki_key_pkcs11_t	The structure that holds the PKI PKCS11 definitions
Ccoap_proxy_list_t
Ccoap_proxy_req_t
Ccoap_proxy_server_list_t
Ccoap_proxy_server_t
Ccoap_queue_t	Queue entry
Ccoap_rblock_t	Structure to keep track of received blocks
Ccoap_resource_t	Abstraction of resource that can be attached to coap_context_t
Ccoap_session_t	Abstraction of virtual session that can be attached to coap_context_t (client) or coap_endpoint_t (server)
Ccoap_sockaddr_un
Ccoap_socket_t
Ccoap_str_const_t	CoAP string data definition with const data
Ccoap_string_t	CoAP string data definition
Ccoap_subscription_t	Number of notifications that may be sent non-confirmable before a confirmable message is sent to detect if observers are alive
Ccoap_tls_version_t	The structure used for returning the underlying (D)TLS library information
Ccoap_uri_info_t
Ccoap_uri_t	Representation of parsed URI
Ccoap_ws_state_t	WebSockets session state
Ccose_alg_desc
Ccose_curve_desc
Ccose_encrypt0_t
Ccose_hkdf_alg_desc
Cerror_desc_t
Chkdf_hmac_algs
Cin6_pktinfo
Cin_pktinfo
Coscore_association_t
Coscore_ctx_t
Coscore_recipient_ctx_t
Coscore_sender_ctx_t
Cpacket_num_interval
CSHA1Context