type
make
as root
./vpnServer
you'll see output like:
TUN device created: vpn0
VPN server waiting for client...
now, set the ip:
ifconfig vpn0 10.2.0.1 netmask 255.255.255.0 up
or with contemporary iproute2 syntax:
ip link set vpn0 up
ip addr add 10.2.0.1/24 dev vpn0
if you need a route
route add -net 10.2.0.0 netmask 255.255.255.0 dev vpn0
as root, so that it would create the interface.
./vpnClient
output:
TUN device created: vpn0
Connected to VPN server.
set the ip:
ifconfig vpn0 10.2.0.2 netmask 255.255.255.0 up
or with contemporary syntax:
ip link set vpn0 up
ip addr add 10.2.0.2/24 dev vpn0
ping each other's ips.
on client, do:
nc -l -p 2020
on server:
nc 10.2.0.2 2020
now run tcpdump:
tcpdump -i eth0 port 5555 -X
if eth0 is the interface you are connected to the other party.
now if you're sending 'aaaaaaa...' from one machine, it becomes KKK on the other, because XOR of a with 42 will be K
ack 245, win 509, options [nop,nop,TS val 3085257361 ecr 1583262159], length 79
0x0000: 4500 0083 565e 4000 4006 6062 c0a8 014d E...V^@.@.`b...M
0x0010: c0a8 0117 15b3 adf4 25a4 2827 ea9a f01a ........%.('....
0x0020: 8018 01fd 842a 0000 0101 080a b7e5 4a91 .....*........J.
0x0030: 5e5e a9cf 6f2a 2a65 625b 6a2a 6a2c f41b ^^..o**eb[j*j,..
0x0040: 2028 2a2b 2028 2a28 87f0 2dce 157e 8169 .(*+.(*(..-..~.i
0x0050: 1b36 e71b aa32 2bdc f2ca 2a2a 2b2b 2220 .6...2+...**++".
0x0060: 5ddc f6f1 61f4 665c 4b4b 4b4b 4b4b 4b4b ]...a.f\KKKKKKKK
0x0070: 4b4b 4b4b 4b4b 4b4b 4b4b 4b4b 4b4b 4b4b KKKKKKKKKKKKKKKK
0x0080: 4b4b 20 KK.