Nothing works through TinyVPN: Orangepi as server -> Android phone as a client

Trying to establish SIP connection through TinyVPN - nothing works.

OrangePi PC has tinyvpn server, compiled from source code.

Android phone has root, Bria Mobile softphone which can work through specific interface, and tinyvpn client. With regular OpenVPN client-server everything works fine. Tried also openvpn+UDPspeeder - SIP works with one-way audio.

Connection goes through router with port forwarding: 3g -> router -> orangePi PC. Connection establishes without problem.

ping -I tun100 10.222.2.1 from android client to server: is ok. ping -I tun100 10.222.2.2 from server to android client: no ping. ping -I tun100 10.222.2.1 from server - trying to ping local IP - no ping.

iptables policy is ACCEPT everywhere.

ip route:

default via 192.168.0.1 dev eth0
10.222.2.2 dev tun100 proto kernel scope link src 10.222.2.1
169.254.0.0/16 dev eth0 scope link metric 1000
192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.103
192.168.50.0/24 via 192.168.50.2 dev tun0
192.168.50.2 dev tun0 proto kernel scope link src 192.168.50.1

ifconfig:

(other interfaces)
.....
tun100: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1500
        inet 10.222.2.1  netmask 255.255.255.255  destination 10.222.2.2
        inet6 fe80::a8ab:4506:f5c3:5f64  prefixlen 64  scopeid 0x20<link>
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 500  (UNSPEC)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 7  bytes 336 (336.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

netstat -nlp:

(other services)
....
udp        0      0 0.0.0.0:8855            0.0.0.0:*                           3204/tinyvpn

ip rule:

0:      from all lookup local
32766:  from all lookup main
32767:  from all lookup default

Part of tinyvpn window log:

[2018-06-18 00:13:59][INFO][report][**.*(my 3G IP address)**.***.***:30284]client-->server:(original:22 pkt;1848 byte) (fec:308 pkt;9548 byte)  server-->client:(original:2 pkt;96 byte) (fec:28 pkt;616 byte)
[2018-06-18 00:14:10][INFO][report][**.***.***.***:30284]client-->server:(original:22 pkt;1848 byte) (fec:308 pkt;9548 byte)  server-->client:(original:2 pkt;96 byte) (fec:28 pkt;616 byte)
[2018-06-18 00:14:20][INFO][report][**.***.***.***:30284]client-->server:(original:22 pkt;1848 byte) (fec:308 pkt;9548 byte)  server-->client:(original:2 pkt;96 byte) (fec:28 pkt;616 byte)

wangyu- / tinyfecVPN

Nothing works through TinyVPN: Orangepi as server -> Android phone as a client #53