The Vps is too old to get a newer OS from the provider.

1. create /etc/apt/sources.list.d/jessie-backports.list, and fill in the following lines

deb http://archive.debian.org/debian jessie-backports main
deb http://archive.debian.org/debian jessie-backports-sloppy main

2. apt-get update -o Acquire::Check-Valid-Until=false
3. apt-get install shadowsocks-libev

the -o Acquire::Check-Valid-Until=false is the key information. Hope it is helpful.

sh -c ‘printf “deb http://deb.debian.org/debian jessie-backports mainn” > /etc/apt/sources.list.d/jessie-backports.list’
sh -c ‘printf “deb http://deb.debian.org/debian jessie-backports-sloppy main” >> /etc/apt/sources.list.d/jessie-backports.list’
apt update
apt -t jessie-backports-sloppy install shadowsocks-libev

apt-get install –no-install-recommends build-essential autoconf libtool libssl-dev libpcre3-dev libev-dev asciidoc xmlto automake
git clone https://github.com/shadowsocks/simple-obfs.git
cd simple-obfs
git submodule update –init –recursive
./autogen.sh
./configure –disable-documentation && make
make install

cd /usr/ports/net/shadowsocks-libev

make install clean;rehash

ee /etc/rc.conf 加入

shadowsocks_libev_enable=”YES”
shadowsocks_libev_flags=”-c /usr/local/etc/shadowsocks-libev/config.json”

在/usr/local/etc/shadowsocks-libev/config.json中加入

{
“server”:”136.0.16.99″,
“server_port”:1234,             //服务端端口
“local_address”: “127.0.0.1”,
“local_port”:4321,                 //客户端端口
“password”:”password”,      //客户端连接密码
“timeout”:300,
“method”:”aes-256-cfb”     //加密方式
}

然后客户端，在本地，用config.json文件内容对shadowsocks-gui进行相应配置并运行客户端，

shadowsocks-gui下载地址：http://sourceforge.net/projects/shadowsocksgui/files/dist/

最后设置浏览器代理。Chrome 推荐使用 SwitchySharp 切换代理设置。把浏览器代理设为下列参数即可：

协议: socks5

地址: 127.0.0.1

端口: 你填的 local_port

service shadowsocks-libev restart

ok应该可以科学上网了