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32 .\" From: @(#)send.2 8.2 (Berkeley) 2/21/94
42 .Nd send a message from a socket
49 .Fn send "int s" "const void *msg" "size_t len" "int flags"
51 .Fn sendto "int s" "const void *msg" "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 address of the target is given by
74 The length of the message is given by
76 If the message is too long to pass atomically through the
77 underlying protocol, the error
80 the message is not transmitted.
82 No indication of failure to deliver is implicit in a
84 Locally detected errors are indicated by a return value of -1.
86 If no messages space is available at the socket to hold
87 the message to be transmitted, then
89 normally blocks, unless the socket has been placed in
90 non-blocking I/O mode.
93 call may be used to determine when it is possible to
98 parameter may include one or more of the following:
100 #define MSG_OOB 0x1 /* process out-of-band data */
101 #define MSG_PEEK 0x2 /* peek at incoming message */
102 #define MSG_DONTROUTE 0x4 /* bypass routing, use direct interface */
103 #define MSG_EOR 0x8 /* data completes record */
104 #define MSG_EOF 0x100 /* data completes transaction */
111 data on sockets that support this notion (e.g.\&
113 the underlying protocol must also support
117 is used to indicate a record mark for protocols which support the
120 requests that the sender side of a socket be shut down, and that an
121 appropriate indication be sent at the end of the specified data;
122 this flag is only implemented for
126 protocol family, and is used to implement Transaction
131 is usually used only by diagnostic or routing programs.
135 for a description of the
139 The call returns the number of characters sent, or -1
140 if an error occurred.
149 An invalid descriptor was specified.
151 The destination address is a broadcast address, and
153 has not been set on the socket.
159 An invalid user space address was specified for a parameter.
161 The socket requires that message be sent atomically,
162 and the size of the message to be sent made this impossible.
164 The socket is marked non-blocking and the requested operation
167 The system was unable to allocate an internal buffer.
168 The operation may succeed when buffers become available.
170 The output queue for a network interface was full.
171 This generally indicates that the interface has stopped sending,
172 but may be caused by transient congestion.
173 .It Bq Er EHOSTUNREACH
174 The remote host was unreachable.
175 .It Bq Er ECONNREFUSED
176 The socket received an ICMP destination unreachable message
177 from the last message sent. This typically means that the
178 receiver is not listening on the remote port.
180 The remote host was down.
182 The remote network was down.
187 doesn't necessarily block until the data has been transferred, it
188 is possible to transfer an open file descriptor across an
195 it before it has actually been sent, the result being that the receiver
196 gets a closed file descriptor. It is left to the application to
197 implement an acknowlegment mechanism to prevent this from happening.
208 function call appeared in