1SENDTO(3P) POSIX Programmer's Manual SENDTO(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 sendto - send a message on a socket
13
15 #include <sys/socket.h>
16 ssize_t sendto(int socket, const void *message, size_t length,
18 int flags, const struct sockaddr *dest_addr,
19 socklen_t dest_len);
20
23 The sendto() function shall send a message through a connection-mode or
24 connectionless-mode socket. If the socket is connectionless-mode, the
25 message shall be sent to the address specified by dest_addr. If the
26 socket is connection-mode, dest_addr shall be ignored.
27 The sendto() function takes the following arguments:
29 socket Specifies the socket file descriptor.
31 message
33 Points to a buffer containing the message to be sent.
34 length Specifies the size of the message in bytes.
36 flags Specifies the type of message transmission. Values of this argu‐
38 ment are formed by logically OR'ing zero or more of the follow‐
39 ing flags:
40 MSG_EOR
42 Terminates a record (if supported by the protocol).
43 MSG_OOB
45 Sends out-of-band data on sockets that support out-of-band data.
46 The significance and semantics of out-of-band data are protocol-
47 specific.
48 dest_addr
51 Points to a sockaddr structure containing the destination
52 address. The length and format of the address depend on the
53 address family of the socket.
54 dest_len
56 Specifies the length of the sockaddr structure pointed to by the
57 dest_addr argument.
58 If the socket protocol supports broadcast and the specified address is
61 a broadcast address for the socket protocol, sendto() shall fail if the
62 SO_BROADCAST option is not set for the socket.
63 The dest_addr argument specifies the address of the target. The length
65 argument specifies the length of the message.
66 Successful completion of a call to sendto() does not guarantee delivery
68 of the message. A return value of -1 indicates only locally-detected
69 errors.
70 If space is not available at the sending socket to hold the message to
72 be transmitted and the socket file descriptor does not have O_NONBLOCK
73 set, sendto() shall block until space is available. If space is not
74 available at the sending socket to hold the message to be transmitted
75 and the socket file descriptor does have O_NONBLOCK set, sendto() shall
76 fail.
77 The socket in use may require the process to have appropriate privi‐
79 leges to use the sendto() function.
80
82 Upon successful completion, sendto() shall return the number of bytes
83 sent. Otherwise, -1 shall be returned and errno set to indicate the
84 error.
85
87 The sendto() function shall fail if:
88 EAFNOSUPPORT
90 Addresses in the specified address family cannot be used with
91 this socket.
92 EAGAIN or EWOULDBLOCK
94 The socket's file descriptor is marked O_NONBLOCK and the
95 requested operation would block.
96 EBADF The socket argument is not a valid file descriptor.
98 ECONNRESET
100 A connection was forcibly closed by a peer.
101 EINTR A signal interrupted sendto() before any data was transmitted.
103 EMSGSIZE
105 The message is too large to be sent all at once, as the socket
106 requires.
107 ENOTCONN
109 The socket is connection-mode but is not connected.
110 ENOTSOCK
112 The socket argument does not refer to a socket.
113 EOPNOTSUPP
115 The socket argument is associated with a socket that does not
116 support one or more of the values set in flags.
117 EPIPE The socket is shut down for writing, or the socket is connec‐
119 tion-mode and is no longer connected. In the latter case, and if
120 the socket is of type SOCK_STREAM, the SIGPIPE signal is gener‐
121 ated to the calling thread.
122 If the address family of the socket is AF_UNIX, then sendto() shall
125 fail if:
126 EIO An I/O error occurred while reading from or writing to the file
128 system.
129 ELOOP A loop exists in symbolic links encountered during resolution of
131 the pathname in the socket address.
132 ENAMETOOLONG
134 A component of a pathname exceeded {NAME_MAX} characters, or an
135 entire pathname exceeded {PATH_MAX} characters.
136 ENOENT A component of the pathname does not name an existing file or
138 the pathname is an empty string.
139 ENOTDIR
141 A component of the path prefix of the pathname in the socket
142 address is not a directory.
143 The sendto() function may fail if:
146 EACCES Search permission is denied for a component of the path prefix;
148 or write access to the named socket is denied.
149 EDESTADDRREQ
151 The socket is not connection-mode and does not have its peer
152 address set, and no destination address was specified.
153 EHOSTUNREACH
155 The destination host cannot be reached (probably because the
156 host is down or a remote router cannot reach it).
157 EINVAL The dest_len argument is not a valid length for the address fam‐
159 ily.
160 EIO An I/O error occurred while reading from or writing to the file
162 system.
163 EISCONN
165 A destination address was specified and the socket is already
166 connected. This error may or may not be returned for connection
167 mode sockets.
168 ENETDOWN
170 The local network interface used to reach the destination is
171 down.
172 ENETUNREACH
174 No route to the network is present.
175 ENOBUFS
177 Insufficient resources were available in the system to perform
178 the operation.
179 ENOMEM Insufficient memory was available to fulfill the request.
181 If the address family of the socket is AF_UNIX, then sendto() may fail
184 if:
185 ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
187 resolution of the pathname in the socket address.
188 ENAMETOOLONG
190 Pathname resolution of a symbolic link produced an intermediate
191 result whose length exceeds {PATH_MAX}.
192 The following sections are informative.
195
197 None.
198
200 The select() and poll() functions can be used to determine when it is
201 possible to send more data.
202
204 None.
205
207 None.
208
210 getsockopt(), poll(), recv(), recvfrom(), recvmsg(), select(), send(),
211 sendmsg(), setsockopt(), shutdown(), socket(), the Base Definitions
212 volume of IEEE Std 1003.1-2001, <sys/socket.h>
213
215 Portions of this text are reprinted and reproduced in electronic form
216 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
217 -- Portable Operating System Interface (POSIX), The Open Group Base
218 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
219 Electrical and Electronics Engineers, Inc and The Open Group. In the
220 event of any discrepancy between this version and the original IEEE and
221 The Open Group Standard, the original IEEE and The Open Group Standard
222 is the referee document. The original Standard can be obtained online
223 at http://www.opengroup.org/unix/online.html .
224IEEE/The Open Group 2003 SENDTO(3P)