[unix-history] / usr / src / lib / libc / sys / send.2

.\" Copyright (c) 1983 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"	@(#)send.2	6.6 (Berkeley) %G%
.\"
.TH SEND 2 ""
.UC 5
.SH NAME
send, sendto, sendmsg \- send a message from a socket
.SH SYNOPSIS
.nf
.ft B
#include <sys/types.h>
#include <sys/socket.h>
.PP
.ft B
cc = send(s, msg, len, flags)
int cc, s;
char *msg;
int len, flags;
.PP
.ft B
cc = sendto(s, msg, len, flags, to, tolen)
int cc, s;
char *msg;
int len, flags;
struct sockaddr *to;
int tolen;
.PP
.ft B
cc = sendmsg(s, msg, flags)
int cc, s;
struct msghdr *msg;
int flags;
.fi
.SH DESCRIPTION
.IR Send ,
.IR sendto ,
and
.I sendmsg
are used to transmit a message to another socket.
.I Send
may be used only when the socket is in a 
.I connected
state, while 
.I sendto
and
.I sendmsg
may be used at any time.
.PP
The address of the target is given by
.I to
with 
.I tolen
specifying its size.
The length of the message is given by
.IR len .
If the message is too long to pass atomically through the
underlying protocol, then the error EMSGSIZE is returned, and
the message is not transmitted.
.PP
No indication of failure to deliver is implicit in a
.IR send .
Return values of \-1 indicate some locally detected errors.
.PP
If no messages space is available at the socket to hold
the message to be transmitted, then
.I send
normally blocks, unless the socket has been placed in
non-blocking I/O mode.
The
.IR select (2)
call may be used to determine when it is possible to
send more data.
.PP
The
.I flags
parameter may include one or more of the following:
.PP
.nf
.RS
.ta \w'#define\ \ 'u +\w'MSG_DONTROUTE\ \ \ 'u +\w'0x\0\0\0\ \ 'u
#define	MSG_OOB	0x1	/* process out-of-band data */
#define	MSG_DONTROUTE	0x4	/* bypass routing, use direct interface */
.RE
.fi
The flag MSG_OOB is used to send \*(lqout-of-band\*(rq
data on sockets that support this notion (e.g. SOCK_STREAM);
the underlying protocol must also support \*(lqout-of-band\*(rq data.
MSG_DONTROUTE is usually used only by diagnostic or routing programs.
.PP
See 
.IR recv (2)
for a description of the
.I msghdr
structure.
.SH "RETURN VALUE
The call returns the number of characters sent, or \-1
if an error occurred.
.SH "ERRORS
.TP 20
[EBADF]
An invalid descriptor was specified.
.TP 20
[ENOTSOCK]
The argument \fIs\fP is not a socket.
.TP 20
[EFAULT]
An invalid user space address was specified for a parameter.
.TP 20
[EMSGSIZE]
The socket requires that message be sent atomically,
and the size of the message to be sent made this impossible.
.TP 20
[EWOULDBLOCK]
The socket is marked non-blocking and the requested operation
would block.
.TP 20
[ENOBUFS]
The system was unable to allocate an internal buffer.
The operation may succeed when buffers become available.
.TP 20
[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.
.SH SEE ALSO
fcntl(2), recv(2), select(2), getsockopt(2), socket(2), write(2)
Commit	Line	Data
da268306 KB	1	.\" Copyright (c) 1983 The Regents of the University of California.
da268306 KB	2	.\" All rights reserved.
7611a06d	3	.\"
91cff1e1	4	.\" %sccs.include.redist.man%
da268306	5	.\"
91cff1e1	6	.\" @(#)send.2 6.6 (Berkeley) %G%
7611a06d	7	.\"
2b8c449b	8	.TH SEND 2 ""
7611a06d KM	9	.UC 5
	10	.SH NAME
	11	send, sendto, sendmsg \- send a message from a socket
	12	.SH SYNOPSIS
	13	.nf
	14	.ft B
	15	#include <sys/types.h>
	16	#include <sys/socket.h>
	17	.PP
	18	.ft B
	19	cc = send(s, msg, len, flags)
	20	int cc, s;
	21	char *msg;
	22	int len, flags;
	23	.PP
	24	.ft B
	25	cc = sendto(s, msg, len, flags, to, tolen)
	26	int cc, s;
	27	char *msg;
	28	int len, flags;
	29	struct sockaddr *to;
	30	int tolen;
	31	.PP
	32	.ft B
	33	cc = sendmsg(s, msg, flags)
	34	int cc, s;
fc04ceb7	35	struct msghdr *msg;
7611a06d KM	36	int flags;
	37	.fi
	38	.SH DESCRIPTION
	39	.IR Send ,
	40	.IR sendto ,
	41	and
	42	.I sendmsg
	43	are used to transmit a message to another socket.
	44	.I Send
	45	may be used only when the socket is in a
	46	.I connected
	47	state, while
	48	.I sendto
	49	and
	50	.I sendmsg
	51	may be used at any time.
	52	.PP
	53	The address of the target is given by
	54	.I to
	55	with
	56	.I tolen
	57	specifying its size.
	58	The length of the message is given by
	59	.IR len .
	60	If the message is too long to pass atomically through the
	61	underlying protocol, then the error EMSGSIZE is returned, and
	62	the message is not transmitted.
	63	.PP
	64	No indication of failure to deliver is implicit in a
	65	.IR send .
	66	Return values of \-1 indicate some locally detected errors.
	67	.PP
	68	If no messages space is available at the socket to hold
	69	the message to be transmitted, then
	70	.I send
	71	normally blocks, unless the socket has been placed in
def9d0f9	72	non-blocking I/O mode.
7611a06d KM	73	The
	74	.IR select (2)
	75	call may be used to determine when it is possible to
	76	send more data.
	77	.PP
	78	The
	79	.I flags
def9d0f9 MK	80	parameter may include one or more of the following:
	81	.PP
	82	.nf
	83	.RS
	84	.ta \w'#define\ \ 'u +\w'MSG_DONTROUTE\ \ \ 'u +\w'0x\0\0\0\ \ 'u
	85	#define MSG_OOB 0x1 /* process out-of-band data */
	86	#define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */
	87	.RE
	88	.fi
	89	The flag MSG_OOB is used to send \(lqout-of-band\(rq
	90	data on sockets that support this notion (e.g. SOCK_STREAM);
	91	the underlying protocol must also support \(lqout-of-band\(rq data.
	92	MSG_DONTROUTE is usually used only by diagnostic or routing programs.
7611a06d KM	93	.PP
	94	See
	95	.IR recv (2)
	96	for a description of the
	97	.I msghdr
	98	structure.
	99	.SH "RETURN VALUE
	100	The call returns the number of characters sent, or \-1
	101	if an error occurred.
	102	.SH "ERRORS
	103	.TP 20
	104	[EBADF]
	105	An invalid descriptor was specified.
	106	.TP 20
	107	[ENOTSOCK]
	108	The argument \fIs\fP is not a socket.
	109	.TP 20
	110	[EFAULT]
	111	An invalid user space address was specified for a parameter.
	112	.TP 20
	113	[EMSGSIZE]
	114	The socket requires that message be sent atomically,
	115	and the size of the message to be sent made this impossible.
	116	.TP 20
	117	[EWOULDBLOCK]
	118	The socket is marked non-blocking and the requested operation
	119	would block.
def9d0f9 MK	120	.TP 20
	121	[ENOBUFS]
	122	The system was unable to allocate an internal buffer.
	123	The operation may succeed when buffers become available.
	124	.TP 20
	125	[ENOBUFS]
	126	The output queue for a network interface was full.
	127	This generally indicates that the interface has stopped sending,
	128	but may be caused by transient congestion.
7611a06d	129	.SH SEE ALSO
def9d0f9	130	fcntl(2), recv(2), select(2), getsockopt(2), socket(2), write(2)