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Annotated edit history of sendto(2) version 1, including all changes. View license author blame.
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1 perry 1 SEND
2 !!!SEND
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 RETURN VALUE
7 ERRORS
8 CONFORMING TO
9 NOTE
10 SEE ALSO
11 ----
12 !!NAME
13
14
15 send, sendto, sendmsg - send a message from a socket
16 !!SYNOPSIS
17
18
19 __#include __
20 #include __
21
22
23 __int send(int__ ''s''__, const void
24 *__''msg''__, size_t__ ''len''__, int__
25 ''flags''__);
26 int sendto(int__ ''s''__, const void
27 *__''msg''__, size_t__ ''len''__, int__
28 ''flags''__, const struct sockaddr *__''to''__,
29 socklen_t__ ''tolen''__);
30 int sendmsg(int__ ''s''__, const struct msghdr
31 *__''msg''__, int__
32 ''flags''__);__
33 !!DESCRIPTION
34
35
36 __Send__, __sendto__, and __sendmsg__ are used to
37 transmit a message to another socket. __Send__ may be
38 used only when the socket is in a ''connected'' state,
39 while __sendto__ and __sendmsg__ may be used at any
40 time.
41
42
43 The address of the target is given by ''to'' with
44 ''tolen'' specifying its size. The length of the message
45 is given by ''len''. If the message is too long to pass
46 atomically through the underlying protocol, the error
47 __EMSGSIZE__ is returned, and the message is not
48 transmitted.
49
50
51 No indication of failure to deliver is implicit in a
52 __send__. Locally detected errors are indicated by a
53 return value of -1.
54
55
56 When the message does not fit into the send buffer of the
57 socket, __send__ normally blocks, unless the socket has
58 been placed in non-blocking I/O mode. In non-blocking mode
59 it would return __EAGAIN__ in this case. The
60 select(2) call may be used to determine when it is
61 possible to send more data.
62
63
64 The ''flags'' parameter is a flagword and can contain the
65 following flags:
66
67
68 __MSG_OOB__
69
70
71 Sends ''out-of-band'' data on sockets that support this
72 notion (e.g. __SOCK_STREAM__); the underlying protocol
73 must also support ''out-of-band'' data.
74
75
76 __MSG_DONTROUTE__
77
78
79 Dont't use a gateway to send out the packet, only send to
80 hosts on directly connected networks. This is usually used
81 only by diagnostic or routing programs. This is only defined
82 for protocol families that route; packet sockets
83 don't.
84
85
86 __MSG_DONTWAIT__
87
88
89 Enables non-blocking operation; if the operation would
90 block, __EAGAIN__ is returned (this can also be enabled
91 using the __O_NONBLOCK__ with the __F_SETFL
92 fcntl(2)).__
93
94
95 __MSG_NOSIGNAL__
96
97
98 Requests not to send __SIGPIPE__ on errors on stream
99 oriented sockets when the other end breaks the connection.
100 The __EPIPE__ error is still returned.
101
102
103 __MSG_CONFIRM__ (Linux 2.3+ only)
104
105
106 Tell the link layer that forward process happened: you got a
107 successful reply from the other side. If the link layer
108 doesn't get this it'll regularly reprobe the neighbour (e.g.
109 via a unicast ARP). Only valid on __SOCK_DGRAM__ and
110 __SOCK_RAW__ sockets and currently only implemented for
111 IPv4 and IPv6. See arp(7) for details.
112
113
114 The definition of the ''msghdr'' structure follows. See
115 recv(2) and below for an exact description of its
116 fields.
117
118
119 struct msghdr {
120 void * msg_name; /* optional address */
121 socklen_t msg_namelen; /* size of address */
122 struct iovec * msg_iov; /* scatter/gather array */
123 size_t msg_iovlen; /* # elements in msg_iov */
124 void * msg_control; /* ancillary data, see below */
125 socklen_t msg_controllen; /* ancillary data buffer len */
126 int msg_flags; /* flags on received message */
127 };
128
129
130 You may send control information using the
131 ''msg_control'' and ''msg_controllen'' members. The
132 maximum control buffer length the kernel can process is
133 limited per socket by the __net.core.optmem_max__ sysctl;
134 see socket(7).
135 !!RETURN VALUE
136
137
138 The calls return the number of characters sent, or -1 if an
139 error occurred.
140 !!ERRORS
141
142
143 These are some standard errors generated by the socket
144 layer. Additional errors may be generated and returned from
145 the underlying protocol modules; see their respective manual
146 pages.
147
148
149 __EBADF__
150
151
152 An invalid descriptor was specified.
153
154
155 __ENOTSOCK__
156
157
158 The argument ''s'' is not a socket.
159
160
161 __EFAULT__
162
163
164 An invalid user space address was specified for a
165 parameter.
166
167
168 __EMSGSIZE__
169
170
171 The socket requires that message be sent atomically, and the
172 size of the message to be sent made this
173 impossible.
174
175
176 __EAGAIN__ or __EWOULDBLOCK__
177
178
179 The socket is marked non-blocking and the requested
180 operation would block.
181
182
183 __ENOBUFS__
184
185
186 The output queue for a network interface was full. This
187 generally indicates that the interface has stopped sending,
188 but may be caused by transient congestion. (This cannot
189 occur in Linux, packets are just silently dropped when a
190 device queue overflows.)
191
192
193 __EINTR__
194
195
196 A signal occurred.
197
198
199 __ENOMEM__
200
201
202 No memory available.
203
204
205 __EINVAL__
206
207
208 Invalid argument passed.
209
210
211 __EPIPE__
212
213
214 The local end has been shut down on a connection oriented
215 socket. In this case the process will also receive a
216 __SIGPIPE__ unless __MSG_NOSIGNAL__ is
217 set.
218 !!CONFORMING TO
219
220
221 4.4BSD, SVr4, POSIX 1003.1g draft (these function calls
222 appeared in 4.2BSD).
223
224
225 __MSG_CONFIRM__ is a Linux extension.
226 !!NOTE
227
228
229 The prototypes given above follow the Single Unix
230 Specification, as glibc2 also does; the ''flags''
231 argument was `int' in BSD 4.*, but `unsigned int' in libc4
232 and libc5; the ''len'' argument was `int' in BSD 4.* and
233 libc4, but `size_t' in libc5; the ''tolen'' argument was
234 `int' in BSD 4.* and libc4 and libc5. See also
235 accept(2).
236 !!SEE ALSO
237
238
239 fcntl(2), recv(2), select(2),
240 getsockopt(2), sendfile(2), socket(2),
241 write(2), socket(7), ip(7),
242 tcp(7), udp(7)
243 ----
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