NAME

       nng_rep - reply protocol

SYNOPSIS

           #include <nng/protocol/reqrep0/rep.h>

DESCRIPTION

       The rep protocol is one half of a request/reply pattern. In this pattern, a requester sends a message to
       one replier, who is expected to reply. The request is resent if no reply arrives, until a reply is
       received or the request times out.

           Tip

           This protocol is useful in setting up RPC-like services. It is also reliable, in that a requester
           will keep retrying until a reply is received.

       The rep protocol is the replier side, and the req protocol is the requester side.

   Socket Operations
       The nng_rep0_open() functions create a replier socket. This socket may be used to receive messages
       (requests), and then to send replies.

       Generally a reply can only be sent after receiving a request.

       Send operations will result in NNG_ESTATE if no corresponding request was previously received.

       Likewise, only one receive operation may be pending at a time. Any additional concurrent receive
       operations will result in NNG_ESTATE.

       Raw mode sockets ignore all these restrictions.

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

       Each context may have at most one outstanding request, and operates independently of the others. 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.)

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

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

SEE ALSO

       nng_rep_open(3), nng(7), nng_req(7)

                                                   2025-04-20                                         NNG_REP(7)