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.\" Modified Fri Jul 23 22:07:54 1993 by Rik Faith <faith@cs.unc.edu>
.\" Modified 950727 by aeb, following a suggestion by Urs Thuermann
.\" <urs@isnogud.escape.de>
.\" Modified Tue Oct 22 08:11:14 EDT 1996 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 1998 by Andi Kleen
.\" 中文版 Copyright (c) 2002 byeyear 和 www.linuxforum.net  
.\"
.TH LISTEN 2 "23 July 1993" "BSD Man Page" "Linux Programmer's Manual"
.SH NAME 名称
listen \- listen for connections on a socket 在一个套接字上倾听连接
.SH SYNOPSIS 概述
.B #include <sys/socket.h>
.sp
.BI "int listen(int " s ", int " backlog );
.SH DESCRIPTION 描述
在接收连接之前,首先要使用
.BR socket (2)
创建一个套接字,然后调用
.BR listen
使其能够自动接收到来的连接并且为连接队列指定一个长度限制.
之后就可以使用
.BR accept (2)
接收连接.
.B listen
调用仅适用于
.B SOCK_STREAM
或者
.BR SOCK_SEQPACKET
类型的套接字.
.PP
参数
.I backlog
指定未完成连接队列的最大长度.如果一个连接请求到达时未完成连接
队列已满,那么客户端将接收到错误
.B ECONNREFUSED.
或者,如果下层协议支持重发,那么这个连接请求将被忽略,这样客户端
在重试的时候就有成功的机会.
.SH NOTES 注意
在TCP套接字中
.I backlog 
的含义在Linux 2.2中已经改变.
它指定了已经完成连接正等待应用程序接收的套接字队列的长度,而不是
未完成连接的数目.未完成连接套接字队列的最大长度可以使用
.B tcp_max_syn_backlog
sysctl设置
当打开syncookies时不存在逻辑上的最大长度,此设置将被忽略.参见
.BR tcp (7)
以获取更多信息.

.SH "RETURN VALUE" "返回值"
函数执行成功时返回0.错误时返回\-1,并置相应错误代码.
.I errno
.SH ERRORS 错误
.TP
.B EBADF
参数
.I s
不是合法的描述符.
.TP
.B ENOTSOCK
参数
.I s
不是一个套接字.
.TP
.B EOPNOTSUPP
套接字类型不支持
.B listen 
操作.
.SH "CONFORMING TO" "兼容于"
Single Unix, 4.4BSD, POSIX 1003.1g.
.B listen
函数调用最初出现于4.2BSD. 
.SH BUGS 勘误
如果套接字类型是 
.BR AF_INET , 
并且参数
.I backlog
大于常量 
.B SOMAXCONN 
(Linux 2.0&2.2中是128),它将被自动截断为
.BR SOMAXCONN
的值. 
有的BSD系统(以及一些BSD扩展)将backlog值限制为5.
.SH "SEE ALSO" "参见"
.BR accept (2),
.BR connect (2),
.BR socket (2)

.SH "[中文版维护人]"
.B byeyear <love_my_love@263.net >
.SH "[中文版最新更新]"
.B 2002.01.27
.SH "《中国linux论坛man手册页翻译计划》:"
.BI http://cmpp.linuxforum.net
.SH "跋"
.br
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.br
中文 man 手册页计划：\fBhttps://github.com/man-pages-zh/manpages-zh\fR