PPTP Client on Ubuntu Server ...

Installing PPTP in Ubuntu Server

sudo apt-get update
sudo apt install pptp-linux

Create PPTP file:

sudo nano /etc/ppp/peers/vpn1

Copy the follwoing texts to your editor:

pty "pptp URL --nolaunchpppd"
name username
password password
remotename PPTP
file /etc/ppp/options.pptp
ipparam pptp-us1

Change the PPTP file permission:

chmod 600 /etc/ppp/peers/vpn1

Command to connect:

pppd call vpn1

UFW Open:

sudo nano /etc/ufw/before.rules

Add the follwoing texts to:

# vpn
-A ufw-before-input -p 47 -j ACCEPT
#-A ufw-before-output -p 47 -j ACCEPT

sudo ufw reload

Second approach is manually loading the nf_conntrack_pptp module. You can do this by running:

sudo modprobe nf_conntrack_pptp