📄 connect.html
字号:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>connect</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4>NAME</h4><blockquote>connect - connect a socket</blockquote><h4>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="syssocket.h.html">sys/socket.h</a>>int connect(int <I>socket</I>, const struct sockaddr *<I>address</I>, socklen_t <I>address_len</I>);</code></pre></blockquote><h4>DESCRIPTION</h4><blockquote>The<i>connect()</i>function requests a connection to be made on a socket. The function takes thefollowing arguments:<dl compact><dt><I>socket</I><dd>Specifies the file descriptor associated with the socket.<dt><I>address</I><dd>Points to a <B>sockaddr</B> structure containing the peer address. The lengthand format of the address depend on the address family of the socket.<dt><I>address_len</I><dd>Specifies the length of the <B>sockaddr</B> structurepointed to by the <I>address</I> argument.</dl><p>If the socket has not already been bound to a local address, <i>connect()</i>will bind it to an address which, unless the socket's address family is AF_UNIX, is an unused local address.<p>If the initiating socket is not connection-mode, then<i>connect()</i>sets the socket's peer address, but no connection is made. For SOCK_DGRAMsockets, the peer address identifies where all datagrams are sent onsubsequent<i><a href="send.html">send()</a></i>calls, and limits the remote sender for subsequent<i><a href="recv.html">recv()</a></i>calls. If <I>address</I> is a null address for the protocol, the socket's peeraddress will be reset.<p>If the initiating socket is connection-mode, then<i>connect()</i>attempts to establish a connection to the address specified by the<I>address</I> argument.<p>If the connection cannot be established immediately and O_NONBLOCK is not setfor the file descriptor for the socket,<i>connect()</i>will block for up to an unspecified timeout interval until theconnection is established. If the timeout interval expires before theconnection is established,<i>connect()</i>will fail and the connection attempt will be aborted. If<i>connect()</i>is interrupted by a signal that is caught while blocked waiting to establish aconnection,<i>connect()</i>will fail and set <I>errno</I> to [EINTR], but the connection request will notbe aborted, and the connection will be established asynchronously.<p>If the connection cannot be established immediately and O_NONBLOCK is set forthe file descriptor for the socket,<i>connect()</i>will fail and set <I>errno</I> to [EINPROGRESS], but the connection requestwill not be aborted, and the connection will be established asynchronously.Subsequent calls to<i>connect()</i>for the same socket, before the connection is established, will fail and set<I>errno</I> to [EALREADY].<p>When the connection has been established asynchronously,<i><a href="select.html">select()</a></i>and<i><a href="poll.html">poll()</a></i>will indicate that the file descriptor for the socket is ready for writing.<p>The socket in use may require the process to have appropriateprivileges to use the<i>connect()</i>function.</blockquote><h4>RETURN VALUE</h4><blockquote>Upon successful completion,<i>connect()</i>returns 0. Otherwise, -1 is returned and <I>errno</I> is set toindicate the error.</blockquote><h4>ERRORS</h4><blockquote>The<i>connect()</i>function will fail if:<dl compact><dt>[EADDRNOTAVAIL]<dd>The specified address is not available from the local machine.<dt>[EAFNOSUPPORT]<dd>The specified address is not a valid address for the address family of thespecified socket.<dt>[EALREADY]<dd>A connection request is already in progress for the specified socket.<dt>[EBADF]<dd>The <I>socket</I> argument is not a valid file descriptor.<dt>[ECONNREFUSED]<dd>The target address was not listening for connections or refused the connectionrequest.<dt>[EFAULT]<dd>The address parameter can not be accessed.<dt>[EINPROGRESS]<dd>O_NONBLOCK is set for the file descriptor for the socket and theconnection cannot be immediately established; the connection will beestablished asynchronously.<dt>[EINTR]<dd>The attempt to establish a connection was interrupted by delivery of a signalthat was caught; the connection will be established asynchronously.<dt>[EISCONN]<dd>The specified socket is connection-mode and is already connected.<dt>[ENETUNREACH]<dd>No route to the network is present.<dt>[ENOTSOCK]<dd>The <I>socket</I> argument does not refer to a socket.<dt>[EPROTOTYPE]<dd>The specified address has a different type than the socket bound to thespecified peer address.<dt>[ETIMEDOUT]<dd>The attempt to connect timed out before a connection was made.</dl><p>If the address family of the socket is AF_UNIX, then<i>connect()</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<I>address</I>.<dt>[ENAMETOOLONG]<dd>A component of a pathname exceeded {NAME_MAX} characters, or anentire pathname exceeded {PATH_MAX} characters.<dt>[ENOENT]<dd>A component of the pathname does not name an existing fileor the pathname is an empty string.<dt>[ENOTDIR]<dd>A component of the path prefix of the pathname in <I>address</I> is not adirectory.</dl><p>The<i>connect()</i>function may fail if:<dl compact><dt>[EACCES]<dd>Search permission is denied for a component of the path prefix; orwrite access to the named socket is denied.<dt>[EADDRINUSE]<dd>Attempt to establish a connection that uses addresses that are already in use.<dt>[ECONNRESET]<dd>Remote host reset the connection request.<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>address_len</I> argument is not a valid length for the address family;or invalid address family in sockaddr structure.<dt>[ENAMETOOLONG]<dd>Pathname resolution of a symbolic link produced an intermediate result whoselength exceeds {PATH_MAX}.<dt>[ENETDOWN]<dd>The local interface used to reach the destination is down.<dt>[ENOBUFS]<dd>No buffer space is available.<dt>[ENOSR]<dd>There were insufficient STREAMS resources available to complete the operation.<dt>[EOPNOTSUPP]<dd>The socket is listening and can not be connected.</dl></blockquote><h4>APPLICATION USAGE</h4><blockquote>If<i>connect()</i>fails, the state of the socket is unspecified. Portable applications shouldclose the file descriptor and create a new socket before attempting toreconnect.</blockquote><h4>SEE ALSO</h4><blockquote><i><a href="accept.html">accept()</a></i>,<i><a href="bind.html">bind()</a></i>,<i><a href="close.html">close()</a></i>,<i><a href="getsockname.html">getsockname()</a></i>,<i><a href="poll.html">poll()</a></i>,<i><a href="select.html">select()</a></i>,<i><a href="send.html">send()</a></i>,<i><a href="shutdown.html">shutdown()</a></i>,<i><a href="socket.html">socket()</a></i>,<i><a href="syssocket.h.html"><sys/socket.h></a></i>.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 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 + -