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28 .\" From: @(#)send.2 8.2 (Berkeley) 2/21/94
29 .\" $FreeBSD: src/lib/libc/sys/send.2,v 1.10.2.6 2001/12/14 18:34:01 ru Exp $
38 .Nd send a message from a socket
45 .Fn send "int s" "const void *msgbuf" "size_t len" "int flags"
47 .Fn sendto "int s" "const void *msgbuf" "size_t len" "int flags" "const struct sockaddr *to" "socklen_t tolen"
49 .Fn sendmsg "int s" "const struct msghdr *msg" "int flags"
55 are used to transmit a message to another socket.
57 may be used only when the socket is in a
63 may be used at any time.
65 The socket file descriptor is given by
68 points to a buffer containing the message.
73 The address of the target is given by
78 The length of the message is given by
80 If the message is too long to pass atomically through the
81 underlying protocol, the error
84 the message is not transmitted.
86 No indication of failure to deliver is implicit in a
88 Locally detected errors are indicated by a return value of -1.
90 If no messages space is available at the socket to hold
91 the message to be transmitted, then
93 normally blocks, unless the socket has been placed in
94 non-blocking I/O mode.
97 call may be used to determine when it is possible to
102 parameter may include one or more of the following:
104 #define MSG_OOB 0x1 /* process out-of-band data */
105 #define MSG_PEEK 0x2 /* peek at incoming message */
106 #define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */
107 #define MSG_EOR 0x8 /* data completes record */
108 #define MSG_EOF 0x100 /* data completes transaction */
109 #define MSG_NOSIGNAL 0x400 /* No SIGPIPE to unconnected socket stream */
116 data on sockets that support this notion (e.g.\&
118 the underlying protocol must also support
122 is used to indicate a record mark for protocols which support the
125 requests that the sender side of a socket be shut down, and that an
126 appropriate indication be sent at the end of the specified data;
127 this flag is only implemented for
133 is usually used only by diagnostic or routing programs.
135 requests not to send the
137 signal if an attempt to
139 is made on a stream-oriented socket that is no longer connected.
143 for a description of the
147 Upon successful completion the number of characters which were sent is
148 returned. Otherwise -1 is returned and the global variable
150 is set to indicate the error.
159 An invalid descriptor was specified.
161 The destination address is a broadcast address, and
163 has not been set on the socket.
169 An invalid user space address was specified for a parameter.
171 The socket requires that message be sent atomically,
172 and the size of the message to be sent made this impossible.
174 The socket is marked non-blocking and the requested operation
177 The system was unable to allocate an internal buffer.
178 The operation may succeed when buffers become available.
180 The output queue for a network interface was full.
181 This generally indicates that the interface has stopped sending,
182 but may be caused by transient congestion.
183 .It Bq Er EHOSTUNREACH
184 The remote host was unreachable.
185 .It Bq Er ECONNREFUSED
186 The socket received an ICMP destination unreachable message
187 from the last message sent. This typically means that the
188 receiver is not listening on the remote port.
190 The remote host was down.
192 The socket is unable to send anymore data (SS_CANTSENDMORE has
193 been set on the socket). This typically means that the socket
206 function call appeared in
211 doesn't necessarily block until the data has been transferred, it
212 is possible to transfer an open file descriptor across an
219 it before it has actually been sent, the result being that the receiver
220 gets a closed file descriptor. It is left to the application to
221 implement an acknowledgment mechanism to prevent this from happening.