'\" t
.\"     Title: nn_recv
.\"    Author: [see the "AUTHOR(S)" section]
.\" Generator: Asciidoctor 2.0.18
.\"      Date: 2021-02-08
.\"    Manual: NNG Reference Manual
.\"    Source: \ \&
.\"  Language: English
.\"
.TH "NN_RECV" "3compat" "2021-02-08" "\ \&" "NNG Reference Manual"
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.SH "NAME"
nn_recv \- receive data (compatible API)
.SH "SYNOPSIS"
.sp
.if n .RS 4
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.fam C
#include <nanomsg/nn.h>

int nn_recv(int sock, void *data, size_t size, int flags)
.fam
.fi
.if n .RE
.SH "DESCRIPTION"
.sp
The \f(CRnn_recv()\fP function receives a message from the socket \fIsock\fP.
The message body must fit within \fIsize\fP bytes, and will be stored
at the location specified by \fIdata\fP, unless \fIsize\fP is the
special value \f(CRNN_MSG\fP, indicating a zero\-copy operation.
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.RS 4
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.B Note
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.sp
This function is provided for API
compatibility with legacy \fIlibnanomsg\fP.
Consider using the relevant modern API instead.
.sp .5v
.RE
.sp
If \fIsize\fP has the special value \f(CRNN_MSG\fP, then a zero\-copy operation
is performed.
In this case, instead of copying the message data into the address
specified by \fIdata\fP, a new message large enough to hold the message data
will be allocated (as if by the
function \f(CRnn_allocmsg()\fP), and the message
payload will be stored accordingly.
In this case, the value stored at \fIdata\fP will not be message data,
but a pointer to the message itself.
In this case, on success, the caller shall take responsibility for
the final disposition of the message (such as by sending it to
another peer using \f(CRnn_send()\fP) or
\f(CRnn_freemsg()\fP.
.sp
The \fIflags\fP field may contain the special flag \f(CRNN_DONTWAIT\fP.
In this case, if the no message is available for immediate receipt,
the operation shall not block, but instead will fail with the error \f(CREAGAIN\fP.
.SH "RETURN VALUES"
.sp
This function returns the number of bytes sent on success, and \-1 on error.
.SH "ERRORS"
.sp
\f(CREAGAIN\fP
.RS 4
The operation would block.
.RE
.sp
\f(CREBADF\fP
.RS 4
The socket \fIsock\fP is not open.
.RE
.sp
\f(CREFSM\fP
.RS 4
The socket cannot receive in this state.
.RE
.sp
\f(CRENOTSUP\fP
.RS 4
This protocol cannot receive.
.RE
.sp
\f(CRETIMEDOUT\fP
.RS 4
Operation timed out.
.RE
.SH "SEE ALSO"
.sp
nn_errno(3compat),
nn_recvmsg(3compat),
nn_send(3compat),
nn_socket(3compat),
nn_compat(3compat),
nng(7)