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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 名稱
listen \- listen for connections on a socket 在一個套接字上傾聽連接
.SH SYNOPSIS 概述
.B #include <sys/socket.h>
.sp
.BI "int listen(int " s ", int " backlog );
.SH DESCRIPTION 描述
在接收連接之前,首先要使用
.BR socket (2)
創建一個套接字,然後調用
.BR listen
使其能夠自動接收到來的連接並且爲連接隊列指定一個長度限制.
之後就可以使用
.BR accept (2)
接收連接.
.B listen
調用僅適用於
.B SOCK_STREAM
或者
.BR SOCK_SEQPACKET
類型的套接字.
.PP
參數
.I backlog
指定未完成連接隊列的最大長度.如果一個連接請求到達時未完成連接
隊列已滿,那麼客戶端將接收到錯誤
.B ECONNREFUSED.
或者,如果下層協議支持重發,那麼這個連接請求將被忽略,這樣客戶端
在重試的時候就有成功的機會.
.SH NOTES 注意
在TCP套接字中
.I backlog 
的含義在Linux 2.2中已經改變.
它指定了已經完成連接正等待應用程序接收的套接字隊列的長度,而不是
未完成連接的數目.未完成連接套接字隊列的最大長度可以使用
.B tcp_max_syn_backlog
sysctl設置
當打開syncookies時不存在邏輯上的最大長度,此設置將被忽略.參見
.BR tcp (7)
以獲取更多信息.

.SH "RETURN VALUE" "返回值"
函數執行成功時返回0.錯誤時返回\-1,並置相應錯誤代碼.
.I errno
.SH ERRORS 錯誤
.TP
.B EBADF
參數
.I s
不是合法的描述符.
.TP
.B ENOTSOCK
參數
.I s
不是一個套接字.
.TP
.B EOPNOTSUPP
套接字類型不支持
.B listen 
操作.
.SH "CONFORMING TO" "兼容於"
Single Unix, 4.4BSD, POSIX 1003.1g.
.B listen
函數調用最初出現於4.2BSD. 
.SH BUGS 勘誤
如果套接字類型是 
.BR AF_INET , 
並且參數
.I backlog
大於常量 
.B SOMAXCONN 
(Linux 2.0&2.2中是128),它將被自動截斷爲
.BR SOMAXCONN
的值. 
有的BSD系統(以及一些BSD擴展)將backlog值限制爲5.
.SH "SEE ALSO" "參見"
.BR accept (2),
.BR connect (2),
.BR socket (2)

.SH "[中文版維護人]"
.B byeyear <love_my_love@263.net >
.SH "[中文版最新更新]"
.B 2002.01.27
.SH "《中國linux論壇man手冊頁翻譯計劃》:"
.BI http://cmpp.linuxforum.net
.SH "跋"
.br
本頁面中文版由中文 man 手冊頁計劃提供。
.br
中文 man 手冊頁計劃：\fBhttps://github.com/man-pages-zh/manpages-zh\fR