aiocoap.numbers.constants module

Constants either defined in the CoAP protocol (often default values for lack of ways to determine eg. the estimated round trip time). Some parameters are invented here for practical purposes of the implementation (eg. DEFAULT_BLOCK_SIZE_EXP, EMPTY_ACK_DELAY).

aiocoap.numbers.constants.COAP_PORT = 5683

The IANA-assigned standard port for COAP services.

aiocoap.numbers.constants.ACK_TIMEOUT = 2.0

The time, in seconds, to wait for an acknowledgement of a confirmable message. The inter-transmission time doubles for each retransmission.

aiocoap.numbers.constants.ACK_RANDOM_FACTOR = 1.5

Timeout multiplier for anti-synchronization.

aiocoap.numbers.constants.MAX_RETRANSMIT = 4

The number of retransmissions of confirmable messages to non-multicast endpoints before the infrastructure assumes no acknowledgement will be received.

aiocoap.numbers.constants.NSTART = 1

Maximum number of simultaneous outstanding interactions that endpoint maintains to a given server (including proxies)

aiocoap.numbers.constants.MAX_TRANSMIT_SPAN = 45.0

Maximum time from the first transmission of a confirmable message to its last retransmission.

aiocoap.numbers.constants.MAX_TRANSMIT_WAIT = 93.0

Maximum time from the first transmission of a confirmable message to the time when the sender gives up on receiving an acknowledgement or reset.

aiocoap.numbers.constants.MAX_LATENCY = 100.0

Maximum time a datagram is expected to take from the start of its transmission to the completion of its reception.

aiocoap.numbers.constants.PROCESSING_DELAY = 2.0

“Time a node takes to turn around a confirmable message into an acknowledgement.

aiocoap.numbers.constants.MAX_RTT = 202.0

Maximum round-trip time.

aiocoap.numbers.constants.EXCHANGE_LIFETIME = 247.0

time from starting to send a confirmable message to the time when an acknowledgement is no longer expected, i.e. message layer information about the message exchange can be purged

aiocoap.numbers.constants.DEFAULT_BLOCK_SIZE_EXP = 6

Default size exponent for blockwise transfers.

aiocoap.numbers.constants.EMPTY_ACK_DELAY = 0.1

After this time protocol sends empty ACK, and separate response

aiocoap.numbers.constants.REQUEST_TIMEOUT = 93.0

Time after which server assumes it won’t receive any answer. It is not defined by IETF documents. For human-operated devices it might be preferable to set some small value (for example 10 seconds) For M2M it’s application dependent.