NAME

       nng_respondent - respondent protocol

SYNOPSIS

           #include <nng/protocol/survey0/respond.h>

DESCRIPTION

       The respondent protocol is one half of a survey pattern. In this pattern, a surveyor sends
       a survey, which is broadcast to all peer respondents. The respondents then have a chance
       to reply (but are not obliged to reply). The survey itself is a timed event, so that
       responses received after the survey has finished are discarded.

           Tip
           This protocol is useful in solving voting problems, such as leader election in cluster
           configurations, as well as certain kinds of service discovery problems.

       The respondent protocol is the respondent side, and the surveyor protocol is the surveyor
       side.

   Socket Operations
       The nng_respondent0_open() functions create a respondent socket. This socket may be used
       to receive messages, and then to send replies. A reply can only be sent after receiving a
       survey, and generally the reply will be sent to surveyor from whom the last survey was
       received.

       Respondents may discard a survey by simply not replying to it.

       Raw mode sockets (set with NNG_OPT_RAW) ignore all these restrictions.

   Context Operations
       This protocol supports the creation of contexts for concurrent use cases using
       nng_ctx_open().

       Incoming surveys will be routed to and received by only one context. Additional surveys
       may be received by other contexts in parallel. Replies made using a context will be
       returned to the the surveyor that issued the survey most recently received by that
       context. The restrictions for order of operations with sockets apply equally well for
       contexts, except that each context will be treated as if it were a separate socket.

   Protocol Versions
       Only version 0 of this protocol is supported. (At the time of writing, no other versions
       of this protocol have been defined. An earlier and incompatible version of the protocol
       was used in older pre-releases of nanomsg <http://nanomsg.org>, but was not released in
       any production version.)

   Protocol Options
       The respondent protocol has no protocol-specific options.

   Protocol Headers
       The respondent protocol uses a backtrace in the header. This is more fully documented in
       the surveyor manual.

SEE ALSO

       nng_respondent_open(3), nng_surveyor(7), nng(7)

                                            2024-10-11                          NNG_RESPONDENT(7)