Sockets Library Functions recv(3SOCKET)
NAME
recv, recvfrom, recvmsg - receive a message from a socket
SYNOPSIS
cc [ flag... ] file... -lsocket -lnsl [ library... ]
#include
#include
#include
ssizet recv(int s, void *buf, sizet len, int flags);
ssizet recvfrom(int s, void *buf, sizet len, int flags,
struct sockaddr *from, socklent *fromlen);
ssizet recvmsg(int s, struct msghdr *msg, int flags);
DESCRIPTION
The recv(), recvfrom(), and recvmsg() functions are used to
receive messages from another socket. The s socket is
created with socket(3SOCKET).
If from is a non-NUL pointer, the source address of the
message is filled in. The value-result parameter fromlen is
initialized to the size of the buffer associated with from
and modified on return to indicate the actual size of the
address stored in the buffer. The length of the message is
returned. If a message is too long to fit in the supplied
buffer, excess bytes may be discarded depending on the type
of socket from which the message is received. See
socket(3SOCKET).
If no messages are available at the socket, the receive call
waits for a message to arrive. If the socket is non-
blocking, -1 is returned with the external variable errno
set to EWOULDBLOCK. See fcntl(2).
For processes on the same host, recvmsg() can be used to
receive a file descriptor from another process, but it can-
not receive ancillary data. See libxnet(3LIB).
If a zero-length buffer is specified for a message, an EOF
condition results that is indistinguishable from the suc-
cessful transfer of a file descriptor. For that reason, one
or more bytes of data should be provided when recvmsg()
passes a file descriptor.
SunOS 5.11 Last change: 20 Aug 2007 1
Sockets Library Functions recv(3SOCKET)
The select(3C) call can be used to determine when more data
arrives.
The flags parameter is formed by an OR operation on one or
more of the following:
MSGOB Read any out-of-band data present on the
socket rather than the regular in-band data.
MSGPEK Peek at the data present on the socket. The
data is returned, but not consumed to allow
a subsequent receive operation to see the
same data.
MSGWAITAL Messages are blocked until the full amount
of data requested is returned. The recv()
function can return a smaller amount of data
if a signal is caught, the connection is
terminated, MSGPEK is specified, or if an
error is pending for the socket.
MSGDONTWAIT Pending messages received on the connection
are returned. If data is unavailable, the
function does not block. This behavior is
the equivalent to specifying ONONBLOCK on
the file descriptor of a socket, except that
write requests are unaffected.
The recvmsg() function call uses a msghdr structure defined
in to minimize the number of directly sup-
plied parameters.
RETURN VALUES
Upon successful completion, these functions return the
number of bytes received. Otherwise, they return -1 and set
errno to indicate the error.
ERORS
The recv(), recvfrom(), and recvmsg() functions return
errors under the following conditions:
EBADF The s file descriptor is invalid.
EINVAL The MSGOB flag is set and no out-of-band
data is available.
SunOS 5.11 Last change: 20 Aug 2007 2
Sockets Library Functions recv(3SOCKET)
EINTR The operation is interrupted by the delivery
of a signal before any data is available to
be received.
EIO An I/O error occurs while reading from or
writing to the file system.
ENOMEM Insufficient user memory is available to
complete operation.
ENOSR Insufficient STREAMS resources are available
for the operation to complete.
ENOTSOCK s is not a socket.
ESTALE A stale NFS file handle exists.
EWOULDBLOCK The socket is marked non-blocking and the
requested operation would block.
ECONREFUSED The requested connection was refused by the
peer. For connected IPv4 and IPv6 datagram
sockets, this indicates that the system
received an ICMP Destination Port Unreach-
able message from the peer.
The recv() and recvfrom() functions fail under the following
conditions:
EINVAL The len argument overflows a ssizet.
The recvmsg() function returns errors under the following
conditions:
EINVAL The msgiovlen member of the msghdr structure
pointed to by msg is less than or equal to 0, or
greater than [IOVMAX}. See Intro(2) for a defini-
tion of [IOVMAX}.
SunOS 5.11 Last change: 20 Aug 2007 3
Sockets Library Functions recv(3SOCKET)
EINVAL One of the iovlen values in the msgiov array
member of the msghdr structure pointed to by msg
is negative, or the sum of the iovlen values in
the msgiov array overflows a ssizet.
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Interface Stability Committed
MT-Level Safe
SEE ALSO
fcntl(2), ioctl(2), read(2), connect(3SOCKET),
getsockopt(3SOCKET), libxnet(3LIB), select(3C),
send(3SOCKET), socket(3SOCKET), socket.h(3HEAD), attri-
butes(5)
SunOS 5.11 Last change: 20 Aug 2007 4
|
