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1.1 root 1: .\" Copyright (c) 1983 The Regents of the University of California.
2: .\" All rights reserved.
3: .\"
4: .\" Redistribution and use in source and binary forms are permitted provided
5: .\" that: (1) source distributions retain this entire copyright notice and
6: .\" comment, and (2) distributions including binaries display the following
7: .\" acknowledgement: ``This product includes software developed by the
8: .\" University of California, Berkeley and its contributors'' in the
9: .\" documentation or other materials provided with the distribution and in
10: .\" all advertising materials mentioning features or use of this software.
11: .\" Neither the name of the University nor the names of its contributors may
12: .\" be used to endorse or promote products derived from this software without
13: .\" specific prior written permission.
14: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
15: .\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
16: .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
17: .\"
18: .\" @(#)send.2 6.6 (Berkeley) 6/23/90
19: .\"
20: .TH SEND 2 "June 23, 1990"
21: .UC 5
22: .SH NAME
23: send, sendto, sendmsg \- send a message from a socket
24: .SH SYNOPSIS
25: .nf
26: .ft B
27: #include <sys/types.h>
28: #include <sys/socket.h>
29: .PP
30: .ft B
31: cc = send(s, msg, len, flags)
32: int cc, s;
33: char *msg;
34: int len, flags;
35: .PP
36: .ft B
37: cc = sendto(s, msg, len, flags, to, tolen)
38: int cc, s;
39: char *msg;
40: int len, flags;
41: struct sockaddr *to;
42: int tolen;
43: .PP
44: .ft B
45: cc = sendmsg(s, msg, flags)
46: int cc, s;
47: struct msghdr *msg;
48: int flags;
49: .fi
50: .SH DESCRIPTION
51: .IR Send ,
52: .IR sendto ,
53: and
54: .I sendmsg
55: are used to transmit a message to another socket.
56: .I Send
57: may be used only when the socket is in a
58: .I connected
59: state, while
60: .I sendto
61: and
62: .I sendmsg
63: may be used at any time.
64: .PP
65: The address of the target is given by
66: .I to
67: with
68: .I tolen
69: specifying its size.
70: The length of the message is given by
71: .IR len .
72: If the message is too long to pass atomically through the
73: underlying protocol, then the error EMSGSIZE is returned, and
74: the message is not transmitted.
75: .PP
76: No indication of failure to deliver is implicit in a
77: .IR send .
78: Return values of \-1 indicate some locally detected errors.
79: .PP
80: If no messages space is available at the socket to hold
81: the message to be transmitted, then
82: .I send
83: normally blocks, unless the socket has been placed in
84: non-blocking I/O mode.
85: The
86: .IR select (2)
87: call may be used to determine when it is possible to
88: send more data.
89: .PP
90: The
91: .I flags
92: parameter may include one or more of the following:
93: .PP
94: .nf
95: .RS
96: .ta \w'#define\ \ 'u +\w'MSG_DONTROUTE\ \ \ 'u +\w'0x\0\0\0\ \ 'u
97: #define MSG_OOB 0x1 /* process out-of-band data */
98: #define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */
99: .RE
100: .fi
101: The flag MSG_OOB is used to send \*(lqout-of-band\*(rq
102: data on sockets that support this notion (e.g. SOCK_STREAM);
103: the underlying protocol must also support \*(lqout-of-band\*(rq data.
104: MSG_DONTROUTE is usually used only by diagnostic or routing programs.
105: .PP
106: See
107: .IR recv (2)
108: for a description of the
109: .I msghdr
110: structure.
111: .SH "RETURN VALUE
112: The call returns the number of characters sent, or \-1
113: if an error occurred.
114: .SH "ERRORS
115: .TP 20
116: [EBADF]
117: An invalid descriptor was specified.
118: .TP 20
119: [ENOTSOCK]
120: The argument \fIs\fP is not a socket.
121: .TP 20
122: [EFAULT]
123: An invalid user space address was specified for a parameter.
124: .TP 20
125: [EMSGSIZE]
126: The socket requires that message be sent atomically,
127: and the size of the message to be sent made this impossible.
128: .TP 20
129: [EWOULDBLOCK]
130: The socket is marked non-blocking and the requested operation
131: would block.
132: .TP 20
133: [ENOBUFS]
134: The system was unable to allocate an internal buffer.
135: The operation may succeed when buffers become available.
136: .TP 20
137: [ENOBUFS]
138: The output queue for a network interface was full.
139: This generally indicates that the interface has stopped sending,
140: but may be caused by transient congestion.
141: .SH SEE ALSO
142: fcntl(2), recv(2), select(2), getsockopt(2), socket(2), write(2)
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