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NNG_RECVMSG(3) NNG Reference Manual NNG_RECVMSG(3)

NAME

nng_recvmsg - receive a message

SYNOPSIS

#include <nng/nng.h>
int nng_recvmsg(nng_socket s, nng_msg **msgp, int flags);

DESCRIPTION

The nng_recvmsg() receives a message on socket s, storing the received message at the location pointed to by msgp.


Tip

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

The flags may contain the following value:

NNG_FLAG_NONBLOCK

The function returns immediately, even if no message is available. Without this flag, the function will wait until a message is received by the socket s, or any configured timer expires.


Note

The semantics of what receiving a message means vary from protocol to
protocol, so examination of the protocol documentation is encouraged. (For example, with an req socket a message may only be received after a request has been sent, and an sub socket may only receive messages corresponding to topics to which it has subscribed.) Furthermore, some protocols may not support receiving data at all, such as pub.

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_ENOMEM

Insufficient memory is available.

NNG_ENOTSUP

The protocol for socket s does not support receiving.

NNG_ESTATE

The socket s cannot receive data in this state.

NNG_ETIMEDOUT

The operation timed out.

SEE ALSO

nng_msg_free(3), nng_recv(3), nng_sendmsg(3), nng_strerror(3), nng_socket(5), nng(7)

2024-10-11