The recv
function is declared in the header file
sys/socket.h. If your flags argument is zero, you can
just as well use read
instead of recv
; see Input and Output Primitives.
ssize_t
recv (int socket, void *buffer, size_t size, int flags)
¶Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
The recv
function is like read
, but with the additional
flags flags. The possible values of flags are described
in Socket Data Options.
If nonblocking mode is set for socket, and no data are available to
be read, recv
fails immediately rather than waiting. See File Status Flags, for information about nonblocking mode.
This function returns the number of bytes received, or -1
on failure.
The following errno
error conditions are defined for this function:
EBADF
The socket argument is not a valid file descriptor.
ENOTSOCK
The descriptor socket is not a socket.
EWOULDBLOCK
Nonblocking mode has been set on the socket, and the read operation
would block. (Normally, recv
blocks until there is input
available to be read.)
EINTR
The operation was interrupted by a signal before any data was read. See Primitives Interrupted by Signals.
ENOTCONN
You never connected this socket.
This function is defined as a cancellation point in multi-threaded programs, so one has to be prepared for this and make sure that allocated resources (like memory, file descriptors, semaphores or whatever) are freed even if the thread is canceled.