Perl getsockopt 函数

描述

此函数获取在套接字实现级别 LEVEL 上为选项 OPTNAME 设置的套接字选项。下表给出了套接字级别 OPTNAME 的一些示例值 -

OPTNAME 	Result
SO_DEBUG 	Get status of recording of debugging information
SO_REUSEADDR 	Get status of local address reuse
SO_KEEPALIVE 	Get status of keep connections alive
SO_DONTROUTE 	Get status of routing bypass for outgoing messages
SO_LINGER 	Get status of linger on close if data is present
SO_BROADCAST 	Get status of permission to transmit broadcast messages
SO_OOBINLINE 	Get status of out-of-band data in band
SO_SNDBUF 	Get buffer size for output
SO_RCVBUF 	Get buffer size for input
SO_TYPE 	Get the type of the socket
SO_ERROR 	Get and clear error on the socket
TCP_NODELAY     To disable the Nagle buffering algorithm.

打包字符串中的具体内容取决于 LEVEL 和 OPTNAME，有关详细信息，请参阅您的系统文档。

句法

以下是该函数的简单语法 -

getsockopt SOCKET, LEVEL, OPTNAME

返回值

该函数在出现错误时返回 undef，否则返回标量上下文中的选项值。

例子

以下是显示其基本用法的示例代码，这将检查 Nagle 算法是否在套接字上打开。但是，在此示例中，您必须打开一个套接字来提供 socked ID -

#!/usr/bin/perl

use Socket qw(:all);

defined(my $tcp = getprotobyname("tcp"))
   or die "Could not determine the protocol number for tcp";
# my $tcp = IPPROTO_TCP; # Alternative

my $packed = getsockopt($socket, $tcp, TCP_NODELAY)
   or die "Could not query TCP_NODELAY socket option: $!";
my $nodelay = unpack("I", $packed);

print "Nagle's algorithm is turned ", $nodelay ? "off\n" : "on\n";