nng_recvmsg(3)

# nng_recvmsg(3) Manual Page

## NAME

nng_recvmsg - recv 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.

| 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.

| 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(7)