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
ssize_t recv(int s, void *buf, size_t len, int flags);
ssize_t recvfrom(int s, void *buf, size_t len, int flags,
struct sockaddr *from, socklen_t *fromlen);
ssize_t 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-NULL 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 callwaits 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, oneor 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:MSG_OOB Read any out-of-band data present on the
socket rather than the regular in-band data.
MSG_PEEK 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.MSG_WAITALL 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 isterminated, MSG_PEEK is specified, or if an
error is pending for the socket.MSG_DONTWAIT Pending messages received on the connection
are returned. If data is unavailable, the function does not block. This behavior isthe equivalent to specifying O_NONBLOCK on
the file descriptor of a socket, except that write requests are unaffected.The recvmsg() function call uses a msghdr structure defined
in
plied parameters.to minimize the number of directly sup- RETURN VALUES
Upon successful completion, these functions return thenumber of bytes received. Otherwise, they return -1 and set
errno to indicate the error.ERRORS
The recv(), recvfrom(), and recvmsg() functions return
errors under the following conditions: EBADF The s file descriptor is invalid.EINVAL The MSG_OOB 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. ECONNREFUSED The requested connection was refused by the peer. For connected IPv4 and IPv6 datagram sockets, this indicates that the systemreceived 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 ssize_t.
The recvmsg() function returns errors under the following
conditions:EINVAL The msg_iovlen member of the msghdr structure
pointed to by msg is less than or equal to 0, orgreater than [IOV_MAX}. See Intro(2) for a defini-
tion of [IOV_MAX}.
SunOS 5.11 Last change: 20 Aug 2007 3
Sockets Library Functions recv(3SOCKET)
EINVAL One of the iov_len values in the msg_iov array
member of the msghdr structure pointed to by msgis negative, or the sum of the iov_len values in
the msg_iov array overflows a ssize_t.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE 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