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recv - receive a message from a connected socket

cc [ flag ... ] file ... -lxnet [ library ... ]
#include <sys/socket.h>

ssize_t recv(int socket, void *buffer, size_t length, int flags);

The recv() function receives a message from a connection-mode or connectionless-mode socket. It is normally used with connected sockets because it does not permit the application to retrieve the source address of received data. The function takes the following arguments:

socket

buffer

length

flags

The recv() function returns the length of the message written to the buffer pointed to by the buffer argument. For message-based sockets such as SOCK_DGRAM and SOCK_SEQPACKET, the entire message must be read in a single operation. If a message is too long to fit in the supplied buffer, and MSG_PEEK is not set in the flags argument, the excess bytes are discarded. For stream-based sockets such as SOCK_STREAM, message boundaries are ignored. In this case, data is returned to the user as soon as it becomes available, and no data is discarded.

If the MSG_WAITALL flag is not set, data will be returned only up to the end of the first message.

If no messages are available at the socket and O_NONBLOCK is not set on the socket's file descriptor, recv() blocks until a message arrives. If no messages are available at the socket and O_NONBLOCK is set on the socket's file descriptor, recv() fails and sets errno to EAGAIN or EWOULDBLOCK.

The recv() function is identical to recvfrom(3XNET) with a zero address_len argument, and to read() if no flags are used.

The select(3C) and poll(2) functions can be used to determine when data is available to be received.

Upon successful completion, recv() returns the length of the message in bytes. If no messages are available to be received and the peer has performed an orderly shutdown, recv() returns 0. Otherwise, -1 is returned and errno is set to indicate the error.

The recv() function will fail if:

EAGAIN

EWOULDBLOCK

EBADF

ECONNRESET

EFAULT

EINTR

EINVAL

ENOTCONN

ENOTSOCK

EOPNOTSUPP

ETIMEDOUT

The recv() function may fail if:

EIO

ENOBUFS

ENOMEM

ENOSR

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Interface Stability	Standard
MT-Level	MT-Safe

poll(2), recvmsg(3XNET), recvfrom(3XNET), select(3C), send(3XNET), sendmsg(3XNET), sendto(3XNET), shutdown(3XNET), socket(3XNET), attributes(5), standards(5)