NAME

       coap_keepalive, coap_context_set_keepalive - work with CoAP keepalive

SYNOPSIS

       #include <coap2/coap.h>

       void void coap_context_set_keepalive(coap_context_t *context, unsigned int seconds);

       Link with -lcoap-2, -lcoap-2-gnutls, -lcoap-2-openssl or -lcoap-2-tinydtls depending on
       your (D)TLS library type.

DESCRIPTION

       There may be a requirement to send out keepalive traffic when the CoAP session is idle (no
       packets have been sent or received for a specified period) to keep, say, an interim NAT
       device "warm" with the NAT translation state, or to periodically check whether the device
       at the other end of the session has "gone away".

       For DTLS, this is done with the confirmable CoAP (0.00) Ping packet, which solicits a CoAP
       RST response. For TLS, this is done with Coap (7.02) Ping packet, which solicits a CoAP
       (7.03) Pong response, all handled by libcoap.

       The coap_context_set_keepalive() function needs to be called to update the context with
       the keepalive for idle traffic timeout of seconds. If seconds is set to 0, then the
       sending of keepalives is disabled. Any sessions created from this context will use the
       same seconds value to determine whether a keepalive "ping" is to be sent out or not.

       Applications can track the usage of the receipt of "pings" and receipt of "responses" by
       defining the respective handlers to use by using coap_register_ping_handler() and
       coap_register_pong_handler().

       If the keepalive fails to solicit a response, then this can be tracked by defining the
       handler to use by using coap_register_nack_handler() which will be called with a reason of
       COAP_NACK_TOO_MANY_RETRIES.

           Note
           coap_context_set_keepalive() is supported by both the CoAP client and CoAP server.

SEE ALSO

       coap_handler(3)

FURTHER INFORMATION

       "RFC7252: The Constrained Application Protocol (CoAP)"

       "RFC8323: CoAP (Constrained Application Protocol) over TCP, TLS, and WebSockets"

BUGS

       Please report bugs on the mailing list for libcoap:
       libcoap-developers@lists.sourceforge.net

AUTHORS

       The libcoap project <libcoap-developers@lists.sourceforge.net>