NAME
send, sendto, sendmsg - send a message from a socket
SYNOPSIS
#include <sys/types.h>
#include <sys/socket.h>
int send(int s, const void *msg, int len unsigned int
flags));
int sendto(int s, const void *msg, int len unsigned int
flags, const struct sockaddr *to, int tolen
int sendmsg(int s, const struct msghdr *msg, unsigned int
flags));
DESCRIPTION
WARNING: This is a BSD man page. As of Linux 0.99.11,
sendmsg was not implemented.
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 specify-
ing 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) call may be used to determine when it is possible
to send more data.
The flags parameter may include one or more of the follow-
ing:
#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
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.
EWOULDBLOCK
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.
CONFORMING TO
4.4BSD, SVr4 (these function calls appeared in 4.2BSD). The
SVr4 versions docoment additional error conditions EINVAL,
EINTR, EMSGSIZE, ENOSR, ENOMEM.
SEE ALSO
fcntl(2), recv(2), select(2), socket(2), write(2)