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32 .\" From: @(#)send.2 8.2 (Berkeley) 2/21/94
33 .\" $FreeBSD: src/lib/libc/sys/send.2,v 1.10.2.6 2001/12/14 18:34:01 ru Exp $
42 .Nd send a message from a socket
49 .Fn send "int s" "const void *msgbuf" "size_t len" "int flags"
51 .Fn sendto "int s" "const void *msgbuf" "size_t len" "int flags" "const struct sockaddr *to" "socklen_t tolen"
53 .Fn sendmsg "int s" "const struct msghdr *msg" "int flags"
59 are used to transmit a message to another socket.
61 may be used only when the socket is in a
67 may be used at any time.
69 The socket file descriptor is given by
72 points to a buffer containing the message.
77 The address of the target is given by
82 The length of the message is given by
84 If the message is too long to pass atomically through the
85 underlying protocol, the error
88 the message is not transmitted.
90 No indication of failure to deliver is implicit in a
92 Locally detected errors are indicated by a return value of -1.
94 If no messages space is available at the socket to hold
95 the message to be transmitted, then
97 normally blocks, unless the socket has been placed in
98 non-blocking I/O mode.
101 call may be used to determine when it is possible to
106 parameter may include one or more of the following:
108 #define MSG_OOB 0x1 /* process out-of-band data */
109 #define MSG_PEEK 0x2 /* peek at incoming message */
110 #define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */
111 #define MSG_EOR 0x8 /* data completes record */
112 #define MSG_EOF 0x100 /* data completes transaction */
113 #define MSG_NOSIGNAL 0x400 /* No SIGPIPE to unconnected socket stream */
120 data on sockets that support this notion (e.g.\&
122 the underlying protocol must also support
126 is used to indicate a record mark for protocols which support the
129 requests that the sender side of a socket be shut down, and that an
130 appropriate indication be sent at the end of the specified data;
131 this flag is only implemented for
137 is usually used only by diagnostic or routing programs.
139 requests not to send the
141 signal if an attempt to
143 is made on a stream-oriented socket that is no longer connected.
147 for a description of the
151 Upon successful completion the number of characters which were sent is
152 returned. Otherwise -1 is returned and the global variable
154 is set to indicate the error.
163 An invalid descriptor was specified.
165 The destination address is a broadcast address, and
167 has not been set on the socket.
173 An invalid user space address was specified for a parameter.
175 The socket requires that message be sent atomically,
176 and the size of the message to be sent made this impossible.
178 The socket is marked non-blocking and the requested operation
181 The system was unable to allocate an internal buffer.
182 The operation may succeed when buffers become available.
184 The output queue for a network interface was full.
185 This generally indicates that the interface has stopped sending,
186 but may be caused by transient congestion.
187 .It Bq Er EHOSTUNREACH
188 The remote host was unreachable.
189 .It Bq Er ECONNREFUSED
190 The socket received an ICMP destination unreachable message
191 from the last message sent. This typically means that the
192 receiver is not listening on the remote port.
194 The remote host was down.
196 The socket is unable to send anymore data (SS_CANTSENDMORE has
197 been set on the socket). This typically means that the socket
210 function call appeared in
215 doesn't necessarily block until the data has been transferred, it
216 is possible to transfer an open file descriptor across an
223 it before it has actually been sent, the result being that the receiver
224 gets a closed file descriptor. It is left to the application to
225 implement an acknowledgment mechanism to prevent this from happening.