How does a CoAP client detect an unsuccessful Put or Get

[mikefoxTB]

What is a good way for a client to detect a failed confirmed request (get or put) as soon as possible? One way is to wait for a response, but this might take two confirmed timeouts or about 3 minutes, however there are a lot of cases where a failed request could be detected sooner, ICMP port closed, non 2xx errors etc. How can a client quickly determine a request did not complete?

[mrdeep1]

You can track this sort of information using an eventor nackhandler - see coap_handler(3). Relying on ICMP (COAP_NACK_ICMP_ISSUE) is unsafe as it may be filtered out by a firewall. Non 2xx responses can get picked up in theresponsehandler. Otherwise, as networks can be 'lossy', it is not safe to assume that 1 missed response means that the server has gone down, but counting COAP_EVENT_MSG_RETRANSMITTEDmay help you here.

[mrdeep1]

@mikefoxTB Closing this issue as information provided. It can be re-opened if there are still questions about this.