SoftEther VPN (Development branch) install script for CentOS 7

Install SoftEther VPN on a fresh CentOS 7 VPS. Opens the necessary ports and set it as a startup service. Use GCC-7 to build

1. Push the two Shell Scripts to your server into the same folder
2. chmod +x softether-install.sh
3. sudo ./softher-install.sh
4. Reboot
5. Check status using systemctl status softether-vpnserver
6. Use SE-VPN Server Manager to config your VPN

su -
cd ~/SoftEtherVPN
git pull
scl enable devtoolset-7 bash
./configure
cd tmp
make
make install
reboot

The Official installation guide is somewhat outdated and unneccessarily complicated. In particualr, an updated CentOS 7 now have firewalld enabled by default, and would reset the old iptable-based rules. Startup script is actually provided using the systemd facility, voiding the need to generate your own init script. (The provided .service file need some patch however, with a single line of sed)

• If you use LetsEncrypt in the same server, shut down SE-Server before getting a new license or renewing. Port 443 is in conflict.
• Client: Use OpenVPN's client. SE-Client for Windows has nasty DNS-leak issue that seems never fixed. (Actually a Windows problem)
• This script makes use of the Development branch repo and build in Release Mode
• This script replaces "cmake" with "cmake3" in the configure script
• A lot of changes happened in 2018, likely break sooner or later