📄 sendto.html

📁 unix 下的C开发手册,还用详细的例程。
💻 HTML
字号:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>sendto</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>sendto - 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 sendto(int <I>socket</I>, const void *<I>message</I>, size_t <I>length</I>, int <I>flags</I>,      const struct sockaddr *<I>dest_addr</I>, socklen_t <I>dest_len</I>);</code></pre></blockquote><h4>DESCRIPTION</h4><blockquote>The<i>sendto()</i>function sends a message through a connection-mode or connectionless-modesocket.  If the socket is connectionless-mode, the message will be sent to theaddress specified by <I>dest_addr</I>.  If the socket is connection-mode,<I>dest_addr</I> is ignored.<p>The function takes the following arguments:<dl compact><dt><I>socket</I><dd>Specifies the socket file descriptor.<dt><I>message</I><dd>Points to a buffer containing the message to be sent.<dt><I>length</I><dd>Specifies the size 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-band data.The significance and semantics of out-of-band data are protocol-specific.</dl><p><dt><I>dest_addr</I><dd>Points to a <B>sockaddr</B> structure containing the destination address.  Thelength and format of the address depend on the address family of the socket.<p><dt><I>dest_len</I><dd>Specifies the length of the <B>sockaddr</B> structurepointed to by the <I>dest_addr</I> argument.<p></dl><p>If the socket protocol supports broadcast and the specified addressis a broadcast address for the socket protocol,<i>sendto()</i>will fail if the SO_BROADCAST option is not set for the socket.<p>The <I>dest_addr</I> argument specifies the address of the target.The <I>length</I> argument specifies the length of the message.<p>Successful completion of a call to<i>sendto()</i>does not guarantee delivery of the message.A return value of -1 indicates only locally-detected errors.<p>If space is not available at the sending socket to holdthe message to be transmitted and the socket file descriptor does not haveO_NONBLOCK set,<i>sendto()</i>blocks until spaceis available.If space is not available at the sending socket to holdthe message to be transmitted and the socket file descriptor does haveO_NONBLOCK set,<i>sendto()</i>will fail.<p>The socket in use may require the process to have appropriateprivileges to use the<i>sendto()</i>function.</blockquote><h4>RETURN VALUE</h4><blockquote>Upon successful completion,<i>sendto()</i>returns the number of bytes sent.  Otherwise, -1 isreturned and <I>errno</I> is set to indicate the error.</blockquote><h4>ERRORS</h4><blockquote>The<i>sendto()</i>function will fail if:<dl compact><dt>[EAFNOSUPPORT]<dd>Addresses in the specified address family cannot be used with this socket.<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>[EFAULT]<dd>The <I>message</I>or <I>destaddr</I>parameter can not be accessed.<dt>[EINTR]<dd>A signal interrupted<i>sendto()</i>before any data was transmitted.<dt>[EMSGSIZE]<dd>The message is too large to be sent all at once, as the socket requires.<dt>[ENOTCONN]<dd>The socket is connection-mode but is not connected.<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>If the address family of the socket is AF_UNIX, then<i>sendto()</i>will fail if:<dl compact><dt>[EIO]<dd>An I/O error occurred while reading from or writing to the file system.<dt>[ELOOP]<dd>Too many symbolic links were encountered in translating the pathname in thesocket address.<dt>[ENAMETOOLONG]<dd>A component of a pathname exceeded {NAME_MAX} characters, or an entirepathname exceeded {PATH_MAX} characters.<dt>[ENOENT]<dd>A component of the pathname does not name an existing file or the pathname isan empty string.<dt>[ENOTDIR]<dd>A component of the path prefix of the pathname in the socket address is not adirectory.</dl><p>The<i>sendto()</i>function may fail if:<dl compact><dt>[EACCES]<dd>Search permission is denied for a component of the path prefix;or write access to the named socket is denied.<dt>[EDESTADDRREQ]<dd>The socket is not connection-mode and does not have its peer address set,and no destination address was specified.<dt>[EHOSTUNREACH]<dd>The destination host cannot be reached (probably because the host is down ora remote router cannot reach it).<dt>[EINVAL]<dd>The <I>dest_len</I> argument is not a valid length for the address family.<dt>[EIO]<dd>An I/O error occurred while reading from or writing to the file system.<dt>[EISCONN]<dd>A destination address was specified and the socketis already connected.<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>[ENOMEM]<dd>Insufficient memory was available to fulfill the request.<dt>[ENOSR]<dd>There were insufficient STREAMS resources available for the operation tocomplete.</dl><p>If the address family of the socket is AF_UNIX, then<i>sendto()</i>may fail if:<dl compact><dt>[ENAMETOOLONG]<dd>Pathname resolution of a symbolic link produced an intermediate result whoselength exceeds {PATH_MAX}.</dl></blockquote><h4>APPLICATION USAGE</h4><blockquote>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.</blockquote><h4>SEE ALSO</h4><blockquote><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="send.html">send()</a></i>,<i><a href="sendmsg.html">sendmsg()</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>
⌨️ 快捷键说明

复制代码 Ctrl + C
搜索代码 Ctrl + F
全屏模式 F11
切换主题 Ctrl + Shift + D
显示快捷键 ?
增大字号 Ctrl + =
减小字号 Ctrl + -