Nginx (“engine x”) 是一个高性能的 HTTP 和 反向代理 服务器，也是一个 IMAP/POP3/SMTP 代理服务器。 Nginx 是由 Igor Sysoev 为俄罗斯访问量第二的 Rambler.ru 站点开发的，第一个公开版本0.1.0发布于2004年10月4日。其将源代码以类BSD许可证的形式发布，因它的稳定性、丰富的功能集、示例配置文件和低系统资源的消耗而闻名。2011年6月1日，nginx 1.0.4发布。 Nginx是一款轻量级的Web 服务器/反向代理服务器及电子邮件（IMAP/POP3）代理服务器，并在一个BSD-like 协议下发行。由俄罗斯的程序设计师Igor Sysoev所开发，供俄国大型的入口网站及搜索引擎Rambler（俄文：Рамблер）使用。其特点是占有内存少，并发能力强，事实上nginx的并发能力确实在同类型的网页服务器中表现较好，中国大陆使用nginx网站用户有：新浪、网易、腾讯等。

nginx-1.9.0 mainline version has been released, with the stream module for generic TCP proxying and load balancing. nginx-1.9.0

Changes with nginx 1.9.0 28 Apr 2015

*) Change: obsolete aio and rtsig event methods have been removed.

*) Feature: the "zone" directive inside the "upstream" block.

*) Feature: the stream module.

*) Feature: byte ranges support in the ngx_http_memcached_module.
   Thanks to Martin Mlynář.

*) Feature: shared memory can now be used on Windows versions with
   address space layout randomization.
   Thanks to Sergey Brester.

*) Feature: the "error_log" directive can now be used on mail and server
   levels in mail proxy.

*) Bugfix: the "proxy_protocol" parameter of the "listen" directive did
   not work if not specified in the first "listen" directive for a
   listen socket.

测试实验：
客户端发送2次hello srv给nginx，nginx轮询分发给server1和server2，再把不同的应答返回给客户端。

client1——\(\)62345\($----server1(12345)\)\(\)\(\)\(|---nginx----| client2------\)\(\)\(\)$$—-server2(12346)

1)nginx 部署轮询方式连接两个tcp服务后端。

#nginx.conf
stream {
    upstream backend {
        #hash $remote_addr consistent;
        #server backend1.example.com:12345 weight=5;
        #server 127.0.0.1:12345 max_fails=3 fail_timeout=30s;
  server 127.0.0.1:12345;
  server 127.0.0.1:12346;
        #server unix:/tmp/backend3;
    }

    server {
        listen 62345;
        proxy_connect_timeout 1s;
        proxy_timeout 3s;
        proxy_pass backend;
    }

}

2)服务端：启动两个server
server.pl 127.0.0.1 12345
server.pl 127.0.0.1 12346

#!/usr/bin/perl -w 
use IO::Socket;
use IO::Select; 

main:
{
  return -1 if(@ARGV < 2);
    my $host = $ARGV[0]; 
    my $port = $ARGV[1]; 
    my $socket = IO::Socket::INET->new(
      LocalAddr => "$host", 
      LocalPort => "$port", 
      Type => SOCK_STREAM, 
      Proto => "tcp", 
      Listen => 200,  #定义listen的最大数
      Blocking => 0,  #非阻塞
    ) or die "Can not create socket connect.$@";

  my $sel = IO::Select->new($socket);
  while (my @ready = $sel->can_read) {
      foreach my $fh (@ready) {
          if ($fh == $socket) {
              my $new = $socket->accept();
              $sel->add($new);
          }else {
              $fh->recv($buffer,1024,0); #接收客户端消息
              print "$buffer \n";
              $fh->send("hello from ".$host.":".$port."\n",0);  #发送服务端消息
              $fh->autoflush(1);
              $sel->remove($fh);
              $fh->close();
            }
        }
    }
  $socket->close() or warn "Close Socket failed.$@";
}

3)客户端：启动两次client
client.pl 127.0.0.1 62345

#!/usr/bin/perl -w 
use strict; 
use IO::Socket; 

main:
{
  return -1 if(@ARGV < 2);
    my $host = $ARGV[0]; 
    my $port = $ARGV[1];  
    my $sock = new IO::Socket::INET( PeerAddr => $host, PeerPort => $port, Proto => 'tcp'); 
    $sock or die "no socket :$!"; 
    my $msg;
    $sock->send("hello srv");
    $sock->recv($msg, 1024);
    print $msg . "\n";
    close $sock;
}

测试结果：
启动两次client,分别收到server1,server2的应答:
hello from 127.0.0.1:12345
hello from 127.0.0.1:12346

正常测试到nginx该版本TCP proxying功能。