NAME

       nng_sendmsg - send message

SYNOPSIS

           #include <nng/nng.h>

           int nng_sendmsg(nng_socket s, nng_msg *msg, int flags);

DESCRIPTION

       The nng_sendmsg() sends message msg using the socket s.

       If the function returns zero, indicating it has accepted the message for delivery, then
       the msg is owned by the socket s, and the caller must not make any further use of it. The
       socket will free the message when it is finished.

       If the function returns non-zero, then it is the caller’s responsibility to dispose of the
       msg, which may include freeing it, sending it to another socket, or simply trying again
       later.

           Tip
           Using this function gives access to the message structure, and may offer more
           functionality than the simpler nng_send() function.

           Note
           The semantics of what sending a message means vary from protocol to protocol, so
           examination of the protocol documentation is encouraged. (For example, with a pub
           socket the data is broadcast, so that any peers who have a suitable subscription will
           be able to receive it using nng_recv() or a similar function.) Furthermore, some
           protocols may not support sending (such as sub) or may require other conditions. (For
           example, rep sockets cannot normally send data, which are responses to requests, until
           they have first received a request.)

       The flags may contain the following value:

       NNG_FLAG_NONBLOCK
           The function returns immediately, regardless of whether the socket is able to accept
           the data or not. If the socket is unable to accept the data (such as if backpressure
           exists because the peers are consuming messages too slowly, or no peer is present),
           then the function will return with NNG_EAGAIN. If this flag is not specified, then the
           function will block if such a condition exists.

           Note
           Regardless of the presence or absence of NNG_FLAG_NONBLOCK, there may be queues
           between the sender and the receiver. Furthermore, there is no guarantee that the
           message has actually been delivered. Finally, with some protocols, the semantic is
           implicitly NNG_FLAG_NONBLOCK, such as with pub sockets, which are best-effort delivery
           only.

RETURN VALUES

       This function returns 0 on success, and non-zero otherwise.

ERRORS

       NNG_EAGAIN
           The operation would block, but NNG_FLAG_NONBLOCK was specified.

       NNG_ECLOSED
           The socket s is not open.

       NNG_EINVAL
           An invalid set of flags was specified.

       NNG_EMSGSIZE
           The value of size is too large.

       NNG_ENOMEM
           Insufficient memory is available.

       NNG_ENOTSUP
           The protocol for socket s does not support sending.

       NNG_ESTATE
           The socket s cannot send data in this state.

       NNG_ETIMEDOUT
           The operation timed out.

SEE ALSO

       nng_msg_alloc(3), nng_recvmsg(3), nng_send(3), nng_strerror(3), nng_msg(5), nng_socket(5),
       nng(7)

                                            2024-10-11                             NNG_SENDMSG(3)