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36 .Nd send message(s) from a socket
42 .Fn send "int s" "const void *msg" "size_t len" "int flags"
44 .Fn sendto "int s" "const void *msg" "size_t len" "int flags" "const struct sockaddr *to" "socklen_t tolen"
46 .Fn sendmsg "int s" "const struct msghdr *msg" "int flags"
48 .Fn sendmmsg "int s" "struct mmsghdr * restrict msgvec" "size_t vlen" "int flags"
60 are used to transmit one or more messages (with the
67 may be used only when the socket is in a
75 may be used at any time if the socket is connectionless-mode.
76 If the socket is connection-mode, the protocol
77 must support implied connect (currently
79 is the only protocol with support) or the socket must be in a
80 connected state before use.
82 The address of the target is given by
86 specifying its size, or the equivalent
92 If the socket is in a connected state, the target address passed to
98 The length of the message is given by
100 If the message is too long to pass atomically through the
101 underlying protocol, the error
104 the message is not transmitted.
108 function sends multiple messages at a call.
109 They are given by the
113 specifying the vector size.
114 The number of octets sent per each message is placed in the
116 field of each processed element of the vector after transmission.
118 No indication of failure to deliver is implicit in a
120 Locally detected errors are indicated by a return value of -1.
122 If no messages space is available at the socket to hold
123 the message to be transmitted, then
125 normally blocks, unless the socket has been placed in
126 non-blocking I/O mode.
129 system call may be used to determine when it is possible to
134 argument may include one or more of the following:
136 #define MSG_OOB 0x00001 /* process out-of-band data */
137 #define MSG_DONTROUTE 0x00004 /* bypass routing, use direct interface */
138 #define MSG_EOR 0x00008 /* data completes record */
139 #define MSG_DONTWAIT 0x00080 /* do not block */
140 #define MSG_EOF 0x00100 /* data completes transaction */
141 #define MSG_NOSIGNAL 0x20000 /* do not generate SIGPIPE on EOF */
148 data on sockets that support this notion (e.g.\&
150 the underlying protocol must also support
154 is used to indicate a record mark for protocols which support the
158 flag request the call to return when it would block otherwise.
160 requests that the sender side of a socket be shut down, and that an
161 appropriate indication be sent at the end of the specified data;
162 this flag is only implemented for
168 is usually used only by diagnostic or routing programs.
172 generation when writing a socket that
177 for a description of the
189 return the number of octets sent.
192 call returns the number of messages sent.
193 If an error occurred a value of -1 is returned.
207 An invalid descriptor was specified.
209 The destination address is a broadcast address, and
211 has not been set on the socket.
213 The socket is connection-mode but is not connected.
219 An invalid user space address was specified for an argument.
221 The socket requires that message be sent atomically,
222 and the size of the message to be sent made this impossible.
224 The socket is marked non-blocking, or
226 is specified, and the requested operation would block.
228 The system was unable to allocate an internal buffer.
229 The operation may succeed when buffers become available.
231 The output queue for a network interface was full.
232 This generally indicates that the interface has stopped sending,
233 but may be caused by transient congestion.
234 .It Bq Er EHOSTUNREACH
235 The remote host was unreachable.
237 A destination address was specified and the socket is already connected.
238 .It Bq Er ECONNREFUSED
239 The socket received an ICMP destination unreachable message
240 from the last message sent.
241 This typically means that the
242 receiver is not listening on the remote port.
244 The remote host was down.
246 The remote network was down.
247 .It Bq Er EADDRNOTAVAIL
250 socket was jailed and the source
251 address specified in the IP header did not match the IP
252 address bound to the prison.
254 The socket is unable to send anymore data
255 .Dv ( SBS_CANTSENDMORE
256 has been set on the socket).
257 This typically means that the socket
281 does not necessarily block until the data has been transferred, it
282 is possible to transfer an open file descriptor across an
289 it before it has actually been sent, the result being that the receiver
290 gets a closed file descriptor.
291 It is left to the application to
292 implement an acknowledgment mechanism to prevent this from happening.