NN_RECVMSG(3) nanomsg manual NN_RECVMSG(3)NAMEnn_recvmsg - fine-grained alternative to nn_recv
SYNOPSIS
#include <nanomsg/nn.h>
NN_EXPORT int nn_recvmsg (int s, struct nn_msghdr *msghdr, int flags);
DESCRIPTION
Receives a message from socket s into buffers specified by msghdr
parameter along with any additional control data. msghdr parameter
should be nullified before being used.
Structure nn_msghdr contains at least following members:
struct nn_iovec *msg_iov;
int msg_iovlen;
void *msg_control;
size_t msg_controllen;
msg_iov points to a gather array of buffers to fill in. msg_iovlen
specifies the size of the array.
msg_control points to the buffer to hold control information associated
with the received message. msg_controllen specifies the length of the
buffer. If the control information should not be retrieved, set
msg_control parameter to NULL. For detailed discussion of how to parse
the control information check nn_cmsg(3) man page.
Structure nn_iovec defines one element in the gather array (a buffer to
be filled in by message data) and contains following members:
void *iov_base;
size_t iov_len;
Alternatively, nanomsg library can allocate the buffer for you. To do
so, let the iov_base point to void* variable to receive the buffer and
set iov_len to NN_MSG. After successful completion user is responsible
for deallocating the message using nn_freemsg(3) function. Gather array
in nn_msghdr structure can contain only one element in this case.
The flags argument is a combination of the flags defined below:
NN_DONTWAIT
Specifies that the operation should be performed in non-blocking
mode. If the message cannot be received straight away, the function
will fail with errno set to EAGAIN.
RETURN VALUE
If the function succeeds number of bytes in the message is returned.
Otherwise, -1 is returned and errno is set to to one of the values
defined below.
ERRORS
EBADF
The provided socket is invalid.
ENOTSUP
The operation is not supported by this socket type.
EFSM
The operation cannot be performed on this socket at the moment
because socket is not in the appropriate state. This error may
occur with socket types that switch between several states.
EAGAIN
Non-blocking mode was requested and there’s no message to receive
at the moment.
EINTR
The operation was interrupted by delivery of a signal before the
message was received.
ETIMEDOUT
Individual socket types may define their own specific timeouts. If
such timeout is hit this error will be returned.
ETERM
The library is terminating.
EXAMPLE
struct nn_msghdr hdr;
struct nn_iovec iov [2];
char buf0 [4];
char buf1 [2];
iov [0].iov_base = buf0;
iov [0].iov_len = sizeof (buf0);
iov [1].iov_base = buf1;
iov [1].iov_len = sizeof (buf1);
memset (&hdr, 0, sizeof (hdr));
hdr.msg_iov = iov;
hdr.msg_iovlen = 2;
nn_recvmsg (s, &hdr, 0);
SEE ALSOnn_recv(3)nn_sendmsg(3)nn_allocmsg(3)nn_freemsg(3)nn_cmsg(3)nanomsg(7)AUTHORS
Martin Sustrik <sustrik@250bpm.com[1]>
NOTES
1. sustrik@250bpm.com
mailto:sustrik@250bpm.com
nanomsg Unknown 12/23/2015 NN_RECVMSG(3)
