高并发，负载均衡，高可用

不要因为技术而技术, 软件工程学需要分层解耦

应用层

1# $$ current process pid
2cd /proc/$$/fd

image-20220320234812684

0 stdin

1 stdout

2 stderr

1# 8 is the name of the file descriptor, <> in and out direction
2exec 8<> /dev/tcp/www.baidu.com/80
3# exec 8<& -
4# & represent the argument is a fd
5echo -e "GET / HTTP/1.0\n" >& 8

image-20220321000400078

传输层