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28 .\" From: @(#)send.2 8.2 (Berkeley) 2/21/94
39 .Nd send message(s) from a socket
45 .Fn send "int s" "const void *msg" "size_t len" "int flags"
47 .Fn sendto "int s" "const void *msg" "size_t len" "int flags" "const struct sockaddr *to" "socklen_t tolen"
49 .Fn sendmsg "int s" "const struct msghdr *msg" "int flags"
51 .Fn sendmmsg "int s" "struct mmsghdr * restrict msgvec" "size_t vlen" "int flags"
63 are used to transmit one or more messages (with the
70 may be used only when the socket is in a
77 may be used at any time.
79 The address of the target is given by
84 The length of the message is given by
86 If the message is too long to pass atomically through the
87 underlying protocol, the error
90 the message is not transmitted.
94 function sends multiple messages at a call.
99 specifying the vector size.
100 The number of octets sent per each message is placed in the
102 field of each processed element of the vector after transmission.
104 No indication of failure to deliver is implicit in a
106 Locally detected errors are indicated by a return value of -1.
108 If no messages space is available at the socket to hold
109 the message to be transmitted, then
111 normally blocks, unless the socket has been placed in
112 non-blocking I/O mode.
115 system call may be used to determine when it is possible to
120 argument may include one or more of the following:
122 #define MSG_OOB 0x00001 /* process out-of-band data */
123 #define MSG_DONTROUTE 0x00004 /* bypass routing, use direct interface */
124 #define MSG_EOR 0x00008 /* data completes record */
125 #define MSG_EOF 0x00100 /* data completes transaction */
126 #define MSG_NOSIGNAL 0x20000 /* do not generate SIGPIPE on EOF */
133 data on sockets that support this notion (e.g.\&
135 the underlying protocol must also support
139 is used to indicate a record mark for protocols which support the
142 requests that the sender side of a socket be shut down, and that an
143 appropriate indication be sent at the end of the specified data;
144 this flag is only implemented for
150 is usually used only by diagnostic or routing programs.
154 generation when writing a socket that
159 for a description of the
171 return the number of octets sent.
174 call returns the number of messages sent.
175 If an error occurred a value of -1 is returned.
189 An invalid descriptor was specified.
191 The destination address is a broadcast address, and
193 has not been set on the socket.
199 An invalid user space address was specified for an argument.
201 The socket requires that message be sent atomically,
202 and the size of the message to be sent made this impossible.
204 The socket is marked non-blocking and the requested operation
207 The system was unable to allocate an internal buffer.
208 The operation may succeed when buffers become available.
210 The output queue for a network interface was full.
211 This generally indicates that the interface has stopped sending,
212 but may be caused by transient congestion.
213 .It Bq Er EHOSTUNREACH
214 The remote host was unreachable.
216 A destination address was specified and the socket is already connected.
217 .It Bq Er ECONNREFUSED
218 The socket received an ICMP destination unreachable message
219 from the last message sent.
220 This typically means that the
221 receiver is not listening on the remote port.
223 The remote host was down.
225 The remote network was down.
226 .It Bq Er EADDRNOTAVAIL
229 socket was jailed and the source
230 address specified in the IP header did not match the IP
231 address bound to the prison.
233 The socket is unable to send anymore data
234 .Dv ( SBS_CANTSENDMORE
235 has been set on the socket).
236 This typically means that the socket
258 does not necessarily block until the data has been transferred, it
259 is possible to transfer an open file descriptor across an
266 it before it has actually been sent, the result being that the receiver
267 gets a closed file descriptor.
268 It is left to the application to
269 implement an acknowledgment mechanism to prevent this from happening.