| SEND(2) |
AerieBSD 1.0 Refernce Manual |
SEND(2) |
NAME
send —
sendto,
sendmsg
send a message from a socket
SYNOPSIS
#include <sys/types.h>
#include <sys/socket.h>
ssize_t
send(int s, const void *msg, size_t len, int flags);
ssize_t
sendto(int s, const void *msg, size_t len, int flags, const struct sockaddr *to, socklen_t tolen);
ssize_t
sendmsg(int s, const struct msghdr *msg, int flags);
DESCRIPTION
send();,
sendto();,
and
sendmsg();
are used to transmit a message to another socket.
send();
may be used only when the socket is in a
connected
state, while
sendto();
and
sendmsg();
may be used at any time.
The address of the target is given by
to
with
tolen
specifying its size.
The length of the message is given by
len.
If the message is too long to pass atomically through the
underlying protocol, the error
EMSGSIZE
is returned, and
the message is not transmitted.
No indication of failure to deliver is implicit in a
send();.
Locally detected errors are indicated by a return value of \-1.
If no messages space is available at the socket to hold
the message to be transmitted, then
send();
normally blocks, unless the socket has been placed in
non-blocking I/O mode.
The
select(2)
or
poll(2)
system calls may be used to determine when it is possible to
send more data.
The
flags
parameter may include one or more of the following:
#define MSG_OOB 0x1 /* process out-of-band data */
#define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */
The flag
MSG_OOB
is used to send
“out-of-band”
data on sockets that support this notion (e.g.,
SOCK_STREAM));
the underlying protocol must also support
“out-of-band”
data.
MSG_DONTROUTE
is usually used only by diagnostic or routing programs.
See
recv(2)
for a description of the
msghdr
structure.
RETURN VALUES
The call returns the number of characters sent, or \-1
if an error occurred.
ERRORS
send();,
sendto();,
and
sendmsg();
fail if:
- [EBADF]
-
An invalid descriptor was specified.
- [ENOTSOCK]
-
The argument
s
is not a socket.
- [EFAULT]
-
An invalid user space address was specified for a parameter.
- [EMSGSIZE]
-
The socket requires that message be sent atomically,
and the size of the message to be sent made this impossible.
- [EAGAIN]
-
The socket is marked non-blocking and the requested operation
would block.
- [ENOBUFS]
-
The system was unable to allocate an internal buffer.
The operation may succeed when buffers become available.
- [ENOBUFS]
-
The output queue for a network interface was full.
This generally indicates that the interface has stopped sending,
but may be caused by transient congestion.
- [EACCES]
-
The
SO_BROADCAST
option is not set on the socket, and a broadcast address
was given as the destination.
- [EHOSTUNREACH]
-
The destination address specified an unreachable host.
- [EINVAL]
-
The
flags
parameter is invalid.
- [EHOSTDOWN]
-
The destination address specified a host that is down.
- [ENETDOWN]
-
The destination address specified a network that is down.
- [ECONNREFUSED]
-
The destination host rejected the message (or a previous one).
This error can only be returned by connected sockets.
- [ENOPROTOOPT]
-
There was a problem sending the message.
This error can only be returned by connected sockets.
- [EDESTADDRREQ]
-
The socket is not connected, and no destination address was specified.
- [EISCONN]
-
The socket is already connected, and a destination address was specified.
In addition,
send();
and
sendto();
may return the following error:
- [EINVAL]
-
len
was larger than
SSIZE_MAX.
Also,
sendmsg();
may return the following errors:
- [EINVAL]
-
The sum of the
iov_len
values in the
msg_iov
array overflowed an
ssize_t.
- [EMSGSIZE]
-
The
msg_iovlen
member of
msg
was less than 0 or larger than
IOV_MAX.
- [EAFNOSUPPORT]
-
Addresses in the specified address family cannot be used with this socket.
SEE ALSO
fcntl(2),
getsockopt(2),
poll(2),
recv(2),
select(2),
socket(2),
write(2),
CMSG_DATA(3)
HISTORY
The
send();
function call appeared in
4.2BSD.
| AerieBSD 1.0 Reference Manual |
August 26 2008 |
SEND(2) |