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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 $
34 .\" $DragonFly: src/lib/libc/sys/send.2,v 1.9 2007/06/30 19:03:52 swildner Exp $
43 .Nd send a message from a socket
50 .Fn send "int s" "const void *msgbuf" "size_t len" "int flags"
52 .Fn sendto "int s" "const void *msgbuf" "size_t len" "int flags" "const struct sockaddr *to" "socklen_t tolen"
54 .Fn sendmsg "int s" "const struct msghdr *msg" "int flags"
60 are used to transmit a message to another socket.
62 may be used only when the socket is in a
68 may be used at any time.
70 The socket file descriptor is given by
73 points to a buffer containing the message.
78 The address of the target is given by
83 The length of the message is given by
85 If the message is too long to pass atomically through the
86 underlying protocol, the error
89 the message is not transmitted.
91 No indication of failure to deliver is implicit in a
93 Locally detected errors are indicated by a return value of -1.
95 If no messages space is available at the socket to hold
96 the message to be transmitted, then
98 normally blocks, unless the socket has been placed in
99 non-blocking I/O mode.
102 call may be used to determine when it is possible to
107 parameter may include one or more of the following:
109 #define MSG_OOB 0x1 /* process out-of-band data */
110 #define MSG_PEEK 0x2 /* peek at incoming message */
111 #define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */
112 #define MSG_EOR 0x8 /* data completes record */
113 #define MSG_EOF 0x100 /* data completes transaction */
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
135 protocol family, and is used to implement Transaction
140 is usually used only by diagnostic or routing programs.
144 for a description of the
148 Upon successful completion the number of characters which were sent is
149 returned. Otherwise -1 is returned and the global variable
151 is set to indicate the error.
160 An invalid descriptor was specified.
162 The destination address is a broadcast address, and
164 has not been set on the socket.
170 An invalid user space address was specified for a parameter.
172 The socket requires that message be sent atomically,
173 and the size of the message to be sent made this impossible.
175 The socket is marked non-blocking and the requested operation
178 The system was unable to allocate an internal buffer.
179 The operation may succeed when buffers become available.
181 The output queue for a network interface was full.
182 This generally indicates that the interface has stopped sending,
183 but may be caused by transient congestion.
184 .It Bq Er EHOSTUNREACH
185 The remote host was unreachable.
186 .It Bq Er ECONNREFUSED
187 The socket received an ICMP destination unreachable message
188 from the last message sent. This typically means that the
189 receiver is not listening on the remote port.
191 The remote host was down.
193 The socket is unable to send anymore data (SS_CANTSENDMORE has
194 been set on the socket). This typically means that the socket
207 function call appeared in
212 doesn't necessarily block until the data has been transferred, it
213 is possible to transfer an open file descriptor across an
220 it before it has actually been sent, the result being that the receiver
221 gets a closed file descriptor. It is left to the application to
222 implement an acknowledgment mechanism to prevent this from happening.