📄 send.html

📁 unix 下的C开发手册,还用详细的例程。
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>send</title></head><body bgcolor=white><center><font size=2>The Single UNIX &reg; Specification, Version 2<br>Copyright &copy; 1997 The Open Group</font></center><hr size=2 noshade><h4>NAME</h4><blockquote>send - send a message on a socket</blockquote><h4>SYNOPSIS</h4><blockquote><pre><code>#include &lt;<a href="syssocket.h.html">sys/socket.h</a>&gt;ssize_t send(int <I>socket</I>, const void *<I>buffer</I>, size_t <I>length</I>, int <I>flags);</I></code></pre></blockquote><h4>DESCRIPTION</h4><blockquote><dl compact><dt><I>socket</I><dd>Specifies the socket file descriptor.<dt><I>buffer</I><dd>Points to the buffer containing the message to send.<dt><I>length</I><dd>Specifies the length of the message in bytes.<dt><I>flags</I><dd>Specifies the type of message transmission.Values of this argument are formed by logically OR'ingzero or more of the following flags:<dl compact><dt>MSG_EOR<dd>Terminates a record (if supported by the protocol)<dt>MSG_OOB<dd>Sends out-of-band data on sockets that support out-of-bandcommunications.The significance and semantics of out-of-band data are protocol-specific.</dl><p></dl><p>The<i>send()</i>function initiates transmission of a message from the specified socket to itspeer.  The<i>send()</i>function sends a message only when the socket is connected(including when the peer of a connectionless socket hasbeen set via<i><a href="connect.html">connect()</a></i>).<p>The length of the message to be sent is specified by the <I>length</I> argument.If the message is too long to pass through the underlying protocol,<i>send()</i>fails and no data is transmitted.<p>Successful completion of a call to<i>send()</i>does not guarantee delivery of the message.  A return value of -1 indicatesonly locally-detected errors.<p>If space is not available at the sending socket to hold the message to betransmitted and the socket file descriptor does not have O_NONBLOCK set,<i>send()</i>blocks until space is available.  If space is not available at the sendingsocket to hold the message to be transmitted and the socket file descriptordoes have O_NONBLOCK set,<i>send()</i>will fail.The<i><a href="select.html">select()</a></i>and<i><a href="poll.html">poll()</a></i>functions can be used to determine when it is possible to send more data.<p>The socket in use may require the process to have appropriateprivileges to use the<i>send()</i>function.</blockquote><h4>RETURN VALUE</h4><blockquote>Upon successful completion,<i>send()</i>returns the number of bytes sent.  Otherwise, -1 isreturned and <I>errno</I> is set to indicate the error.</blockquote><h4>APPLICATION USAGE</h4><blockquote>The<i>send()</i>function is identical to<i><a href="sendto.html">sendto()</a></i>with a null pointer <I>dest_len</I> argument, and to<i><a href="write.html">write()</a></i>if no flags are used.</blockquote><h4>ERRORS</h4><blockquote>The<i>send()</i>function will fail if:<dl compact><dt>[EAGAIN] or [EWOULDBLOCK]<dd><br>The socket's file descriptor is marked O_NONBLOCK and the requested operationwould block.<dt>[EBADF]<dd>The <I>socket</I> argument is not a valid file descriptor.<dt>[ECONNRESET]<dd>A connection was forcibly closed by a peer.<dt>[EDESTADDRREQ]<dd>The socket is not connection-mode and no peer address is set.<dt>[EFAULT]<dd>The <I>buffer</I>parameter can not be accessed. <dt>[EINTR]<dd>A signal interrupted<i>send()</i>before any data was transmitted.<dt>[EMSGSIZE]<dd>The message is too large be sent all at once, as the socket requires.<dt>[ENOTCONN]<dd>The socket is not connected or otherwise has not had the peer prespecified.<dt>[ENOTSOCK]<dd>The <I>socket</I> argument does not refer to a socket.<dt>[EOPNOTSUPP]<dd>The <I>socket</I> argument is associated with a socket that does notsupport one or more of the values set in <I>flags</I>.<dt>[EPIPE]<dd>The socket is shut down for writing, or the socket isconnection-mode and is no longer connected.In the latter case, and if the socket is of type SOCK_STREAM, the SIGPIPEsignal is generated to the calling process.</dl><p>The<i>send()</i>function may fail if:<dl compact><dt>[EACCES]<dd>The calling process does not have the appropriate privileges.<dt>[EIO]<dd>An I/O error occurred while reading from or writing to the file system.<dt>[ENETDOWN]<dd>The local interface used to reach the destination is down.<dt>[ENETUNREACH]<dd>No route to the network is present.<dt>[ENOBUFS]<dd>Insufficient resources were available in the system to perform the operation.<dt>[ENOSR]<dd>There were insufficient STREAMS resources available for the operation tocomplete.</dl></blockquote><h4>SEE ALSO</h4><blockquote><i><a href="connect.html">connect()</a></i>,<i><a href="getsockopt.html">getsockopt()</a></i>,<i><a href="poll.html">poll()</a></i>,<i><a href="recv.html">recv()</a></i>,<i><a href="recvfrom.html">recvfrom()</a></i>,<i><a href="recvmsg.html">recvmsg()</a></i>,<i><a href="select.html">select()</a></i>,<i><a href="sendmsg.html">sendmsg()</a></i>,<i><a href="sendto.html">sendto()</a></i>,<i><a href="setsockopt.html">setsockopt()</a></i>,<i><a href="shutdown.html">shutdown()</a></i>,<i><a href="socket.html">socket()</a></i>,<i><a href="syssocket.h.html">&lt;sys/socket.h&gt;</a></i>.</blockquote><hr size=2 noshade><center><font size=2>UNIX &reg; is a registered Trademark of The Open Group.<br>Copyright &copy; 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>
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