#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);
are used to transmit a message to another socket.
may be used only when the socket is in a
may be used at any time.
The address of the target is given by
specifying its size.
The length of the message is given by
Fa len .
If the message is too long to pass atomically through the
underlying protocol, the error
is returned, and
the message is not transmitted.
No indication of failure to deliver is implicit in a
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
normally blocks, unless the socket has been placed in
non-blocking I/O mode.
system call may be used to determine when it is possible to
send more data.
argument may include one or more of the following:
#define MSG_OOB 0x00001 /* process out-of-band data */
#define MSG_DONTROUTE 0x00004 /* bypass routing, use direct interface */
#define MSG_EOR 0x00008 /* data completes record */
#define MSG_EOF 0x00100 /* data completes transaction */
#define MSG_NOSIGNAL 0x20000 /* do not generate SIGPIPE on EOF */
is used to send
data on sockets that support this notion (e.g.
the underlying protocol must also support
is used to indicate a record mark for protocols which support the
requests that the sender side of a socket be shut down, and that an
appropriate indication be sent at the end of the specified data;
this flag is only implemented for
sockets in the
is usually used only by diagnostic or routing programs.
is used to prevent
generation when writing a socket that
may be closed.
for a description of the
The call returns the number of characters sent, or -1
if an error occurred.
Bq Er EBADF
An invalid descriptor was specified.
Bq Er EACCES
The destination address is a broadcast address, and
has not been set on the socket.
Bq Er ENOTSOCK
is not a socket.
Bq Er EFAULT
An invalid user space address was specified for an argument.
Bq Er EMSGSIZE
The socket requires that message be sent atomically,
and the size of the message to be sent made this impossible.
Bq Er EAGAIN
The socket is marked non-blocking and the requested operation
Bq Er ENOBUFS
The system was unable to allocate an internal buffer.
The operation may succeed when buffers become available.
Bq Er 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.
Bq Er EHOSTUNREACH
The remote host was unreachable.
Bq Er EISCONN
A destination address was specified and the socket is already connected.
Bq Er ECONNREFUSED
The socket received an ICMP destination unreachable message
from the last message sent.
This typically means that the
receiver is not listening on the remote port.
Bq Er EHOSTDOWN
The remote host was down.
Bq Er ENETDOWN
The remote network was down.
Bq Er EPERM
The process using a
socket was jailed and the source
address specified in the IP header did not match the IP
address bound to the prison.
Bq Er EPIPE
The socket is unable to send anymore data
has been set on the socket).
This typically means that the socket
is not connected.
does not necessarily block until the data has been transferred, it
is possible to transfer an open file descriptor across an
it before it has actually been sent, the result being that the receiver
gets a closed file descriptor.
It is left to the application to
implement an acknowledgment mechanism to prevent this from happening.