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46 .TH SENDMSG 3XNET "Nov 1, 2003"
47 .SH NAME
48 sendmsg \- send a message on a socket using a message structure
49 .SH SYNOPSIS
50 .LP
51 .nf
52 \fBcc\fR [ \fIflag\fR ... ] \fIfile\fR ... \fB-lxnet\fR [ \fIlibrary\fR ... ]
53 #include <sys/socket.h>
55 \fBssize_t\fR \fBsendmsg\fR(\fBint\fR \fIsocket\fR, \fBconst struct msghdr *\fR\fImessage\fR, \fBint\fR \fIflags\fR);
56 .fi
58 .SH PARAMETERS
59 .sp
60 .LP
61 The function takes the following arguments:
62 .sp
63 .ne 2
64 .na
65 \fB\fIsocket\fR\fR
66 .ad
67 .RS 11n
68 Specifies the socket file descriptor.
69 .RE
71 .sp
72 .ne 2
73 .na
74 \fB\fImessage\fR\fR
75 .ad
76 .RS 11n
77 Points to a \fBmsghdr\fR structure, containing both the destination address and
78 the buffers for the outgoing message. The length and format of the address
79 depend on the address family of the socket. The \fBmsg_flags\fR member is
80 ignored.
81 .RE
83 .sp
84 .ne 2
85 .na
86 \fB\fIflags\fR\fR
87 .ad
88 .RS 11n
89 Specifies the type of message transmission. The application may specify 0 or
90 the following flag:
91 .sp
92 .ne 2
93 .na
94 \fBMSG_EOR\fR
95 .ad
96 .RS 11n
97 Terminates a record (if supported by the protocol)
98 .RE
100 .sp
101 .ne 2
102 .na
103 \fBMSG_OOB\fR
104 .ad
105 .RS 11n
106 Sends out-of-band data on sockets that support out-of-bound data. The
107 significance and semantics of out-of-band data are protocol-specific.
108 .RE
110 .RE
112 .SH DESCRIPTION
113 .sp
114 .LP
115 The \fBsendmsg()\fR function sends a message through a connection-mode or
116 connectionless-mode socket. If the socket is connectionless-mode, the message
117 will be sent to the address specified by \fImsghdr\fR. If the socket is
118 connection-mode, the destination address in \fImsghdr\fR is ignored.
119 .sp
120 .LP
121 The \fImsg_iov\fR and \fImsg_iovlen\fR fields of message specify zero or more
122 buffers containing the data to be sent. \fImsg_iov\fR points to an array of
123 \fBiovec\fR structures; \fImsg_iovlen\fR must be set to the dimension of this
124 array. In each \fBiovec\fR structure, the \fIiov_base\fR field specifies a
125 storage area and the \fIiov_len\fR field gives its size in bytes. Some of
126 these sizes can be zero. The data from each storage area indicated by
127 \fImsg_iov\fR is sent in turn.
128 .sp
129 .LP
130 Successful completion of a call to \fBsendmsg()\fR does not guarantee delivery
131 of the message. A return value of \(mi1 indicates only locally-detected errors.
132 .sp
133 .LP
134 If space is not available at the sending socket to hold the message to be
135 transmitted and the socket file descriptor does not have \fBO_NONBLOCK\fR set,
136 \fBsendmsg()\fR function blocks until space is available. If space is not
137 available at the sending socket to hold the message to be transmitted and the
138 socket file descriptor does have \fBO_NONBLOCK\fR set, \fBsendmsg()\fR function
139 will fail.
140 .sp
141 .LP
142 If the socket protocol supports broadcast and the specified address is a
143 broadcast address for the socket protocol, \fBsendmsg()\fR will fail if the
144 \fBSO_BROADCAST\fR option is not set for the socket.
145 .sp
146 .LP
147 The socket in use may require the process to have appropriate privileges to use
148 the \fBsendmsg()\fR function.
149 .SH USAGE
150 .sp
151 .LP
152 The \fBselect\fR(3C) and \fBpoll\fR(2) functions can be used to determine when
153 it is possible to send more data.
154 .SH RETURN VALUES
155 .sp
156 .LP
157 Upon successful completion, \fBsendmsg()\fR function returns the number of
158 bytes sent. Otherwise, \(mi1 is returned and \fBerrno\fR is set to indicate
159 the error.
160 .SH ERRORS
161 .sp
162 .LP
163 The \fBsendmsg()\fR function will fail if:
164 .sp
165 .ne 2
166 .na
167 \fB\fBEAGAIN\fR \fR
168 .ad
169 .br
170 .na
171 \fB\fBEWOULDBLOCK\fR\fR
172 .ad
173 .RS 16n
174 The socket's file descriptor is marked O_NONBLOCK and the requested operation
175 would block.
176 .RE
178 .sp
179 .ne 2
180 .na
181 \fB\fBEAFNOSUPPORT\fR\fR
182 .ad
183 .RS 16n
184 Addresses in the specified address family cannot be used with this socket.
185 .RE
187 .sp
188 .ne 2
189 .na
190 \fB\fBEBADF\fR\fR
191 .ad
192 .RS 16n
193 The \fIsocket\fR argument is not a valid file descriptor.
194 .RE
196 .sp
197 .ne 2
198 .na
199 \fB\fBECONNRESET\fR\fR
200 .ad
201 .RS 16n
202 A connection was forcibly closed by a peer.
203 .RE
205 .sp
206 .ne 2
207 .na
208 \fB\fBEFAULT\fR\fR
209 .ad
210 .RS 16n
211 The \fImessage\fR parameter, or storage pointed to by the \fImsg_name\fR,
212 \fImsg_control\fR or \fImsg_iov\fR fields of the \fImessage\fR parameter, or
213 storage pointed to by the \fBiovec\fR structures pointed to by the
214 \fImsg_iov\fR field can not be accessed.
215 .RE
217 .sp
218 .ne 2
219 .na
220 \fB\fBEINTR\fR\fR
221 .ad
222 .RS 16n
223 A signal interrupted \fBsendmsg()\fR before any data was transmitted.
224 .RE
226 .sp
227 .ne 2
228 .na
229 \fB\fBEINVAL\fR\fR
230 .ad
231 .RS 16n
232 The sum of the \fBiov_len\fR values overflows an \fBssize_t\fR.
233 .RE
235 .sp
236 .ne 2
237 .na
238 \fB\fBEMSGSIZE\fR\fR
239 .ad
240 .RS 16n
241 The message is to large to be sent all at once (as the socket requires), or the
242 \fBmsg_iovlen\fR member of the \fBmsghdr\fR structure pointed to by
243 \fImessage\fR is less than or equal to 0 or is greater than \fBIOV_MAX\fR.
244 .RE
246 .sp
247 .ne 2
248 .na
249 \fB\fBENOTCONN\fR\fR
250 .ad
251 .RS 16n
252 The socket is connection-mode but is not connected.
253 .RE
255 .sp
256 .ne 2
257 .na
258 \fB\fBENOTSOCK\fR\fR
259 .ad
260 .RS 16n
261 The \fIsocket\fR argument does not refer a socket.
262 .RE
264 .sp
265 .ne 2
266 .na
267 \fB\fBEOPNOTSUPP\fR\fR
268 .ad
269 .RS 16n
270 The \fIsocket\fR argument is associated with a socket that does not support one
271 or more of the values set in \fIflags\fR.
272 .RE
274 .sp
275 .ne 2
276 .na
277 \fB\fBEPIPE\fR\fR
278 .ad
279 .RS 16n
280 The socket is shut down for writing, or the socket is connection-mode and is no
281 longer connected. In the latter case, and if the socket is of type SOCK_STREAM,
282 the \fBSIGPIPE\fR signal is generated to the calling thread.
283 .RE
285 .sp
286 .LP
287 If the address family of the socket is \fBAF_UNIX\fR, then \fBsendmsg()\fR will
288 fail if:
289 .sp
290 .ne 2
291 .na
292 \fB\fBEIO\fR\fR
293 .ad
294 .RS 16n
295 An I/O error occurred while reading from or writing to the file system.
296 .RE
298 .sp
299 .ne 2
300 .na
301 \fB\fBELOOP\fR\fR
302 .ad
303 .RS 16n
304 Too many symbolic links were encountered in translating the pathname in the
305 socket address.
306 .RE
308 .sp
309 .ne 2
310 .na
311 \fB\fBENAMETOOLONG\fR\fR
312 .ad
313 .RS 16n
314 A component of a pathname exceeded \fINAME_MAX\fR characters, or an entire
315 pathname exceeded \fIPATH_MAX\fR characters.
316 .RE
318 .sp
319 .ne 2
320 .na
321 \fB\fBENOENT\fR\fR
322 .ad
323 .RS 16n
324 A component of the pathname does not name an existing file or the pathname is
325 an empty string.
326 .RE
328 .sp
329 .ne 2
330 .na
331 \fB\fBENOTDIR\fR\fR
332 .ad
333 .RS 16n
334 A component of the path prefix of the pathname in the socket address is not a
335 directory.
336 .RE
338 .sp
339 .LP
340 The \fBsendmsg()\fR function may fail if:
341 .sp
342 .ne 2
343 .na
344 \fB\fBEACCES\fR\fR
345 .ad
346 .RS 16n
347 Search permission is denied for a component of the path prefix; or write access
348 to the named socket is denied.
349 .RE
351 .sp
352 .ne 2
353 .na
354 \fB\fBEDESTADDRREQ\fR\fR
355 .ad
356 .RS 16n
357 The socket is not connection-mode and does not have its peer address set, and
358 no destination address was specified.
359 .RE
361 .sp
362 .ne 2
363 .na
364 \fB\fBEHOSTUNREACH\fR\fR
365 .ad
366 .RS 16n
367 The destination host cannot be reached (probably because the host is down or a
368 remote router cannot reach it).
369 .RE
371 .sp
372 .ne 2
373 .na
374 \fB\fBEIO\fR\fR
375 .ad
376 .RS 16n
377 An I/O error occurred while reading from or writing to the file system.
378 .RE
380 .sp
381 .ne 2
382 .na
383 \fB\fBEISCONN\fR\fR
384 .ad
385 .RS 16n
386 A destination address was specified and the socket is already connected.
387 .RE
389 .sp
390 .ne 2
391 .na
392 \fB\fBENETDOWN\fR\fR
393 .ad
394 .RS 16n
395 The local interface used to reach the destination is down.
396 .RE
398 .sp
399 .ne 2
400 .na
401 \fB\fBENETUNREACH\fR\fR
402 .ad
403 .RS 16n
404 No route to the network is present.
405 .RE
407 .sp
408 .ne 2
409 .na
410 \fB\fBENOBUFS\fR\fR
411 .ad
412 .RS 16n
413 Insufficient resources were available in the system to perform the operation.
414 .RE
416 .sp
417 .ne 2
418 .na
419 \fB\fBENOMEM\fR\fR
420 .ad
421 .RS 16n
422 Insufficient memory was available to fulfill the request.
423 .RE
425 .sp
426 .ne 2
427 .na
428 \fB\fBENOSR\fR\fR
429 .ad
430 .RS 16n
431 There were insufficient STREAMS resources available for the operation to
432 complete.
433 .RE
435 .sp
436 .LP
437 If the address family of the socket is \fBAF_UNIX\fR, then \fBsendmsg()\fR may
438 fail if:
439 .sp
440 .ne 2
441 .na
442 \fB\fBENAMETOOLONG\fR\fR
443 .ad
444 .RS 16n
445 Pathname resolution of a symbolic link produced an intermediate result whose
446 length exceeds \fIPATH_MAX\fR.
447 .RE
449 .SH ATTRIBUTES
450 .sp
451 .LP
452 See \fBattributes\fR(5) for descriptions of the following attributes:
453 .sp
455 .sp
456 .TS
457 box;
458 c | c
459 l | l .
460 ATTRIBUTE TYPE ATTRIBUTE VALUE
461 _
462 Interface Stability Standard
463 _
464 MT-Level MT-Safe
465 .TE
467 .SH SEE ALSO
468 .sp
469 .LP
470 \fBpoll\fR(2) \fBgetsockopt\fR(3XNET), \fBrecv\fR(3XNET),
471 \fBrecvfrom\fR(3XNET), \fBrecvmsg\fR(3XNET), \fBselect\fR(3C),
472 \fBsend\fR(3XNET), \fBsendto\fR(3XNET), \fBsetsockopt\fR(3XNET),
473 \fBshutdown\fR(3XNET), \fBsocket\fR(3XNET), \fBattributes\fR(5),
474 \fBstandards\fR(5)