Client can't reach port-forwarded server application

[Octopus01 2]

Hello,

this is my first day using AirVPN, seems a good and fast service, but I have a problem:

 

I have a server application which listens to port 2405. I have forwarded that port using AirVPN, ran a test using canyouseeme.org and AirVPN, they both can see the service on that port. 

 

Problem is, I don't receive any connection from a client app, connecting in this case to octopus.airdns.org, port 2405. Syn gets sent by the client, and then, nothing.

 

What is the problem?

 

Thanks in advance!

 

[Octopus01 2]

I have also tried to connect locally the client to my server using both

 

10.x.x.x which is VPN interface internal IP

192.168.x.x which is my Wireless interface IP

 

connection is established with no problems. But when I try to connect the client to my external IP / DNS, I get no answer, even if port is in listening and reachable from outside 

[Staff 10014]

Hello!

 

It's quite puzzling (unless it's an FTP server). Which service is it?

 

Kind regards

[Octopus01 2]

It is a client-server application coded by myself. Works normally without VPN.

I even tried with your Port Forwarding Tester: I ran two instances of it, one acting like a listening server, the other one connecting through the DDNS provided by you. The connection attempt failed, as you can see from following image, but tests show that port is forwarded and the DNS responds to ping request.