Network prog : visible from web but not from my app

[Zaap]

Hi,

I made a program which allow a server and a client side to communicate. It works perfectly with local addresses (192.168.xxx.xxx), but when it comes to pass by internet, I have some troubles.

I can see my service on https://canyouseeme.org/. (the connection also appear on my server screen)
I can't see my service using internet browser with public ip (I use the good port of course).
I can't connect to the server from my client using the public ip.

I already disabled firewall and I did a port forwarding on 9696 (my server port).
My client don't have any specified port.

Thanks for help.

[salem c]

> I can't see my service using internet browser with public ip (I use the good port of course).
What do you actually type into your browser URL bar?

What protocol is your server expecting to negotiate? http, telnet, something else?
If it's non-standard, then a browser might not help much.

Did you specify your non-standard port, along with the IP address?
http://216.58.198.164:9696

[Zaap]

I use my self-made protocol (TCP family).
I type:
local:192.168.100.13:9696
public:xxx.xxx.xxx.xxx:9696

Actually I tried to connect to my server with the browser only to check the connectability, but I want my client to be able to connect with.

I precise I'm on windows, using winsock.

[salem c]

Given that canyouseeme seems to work, I'm not sure.

You could use telnet to try to connect to the port via the public address.
https://social.technet.microsoft.com/wiki/contents/articles/38433.windows-10-enabling-telnet-client.aspx
So long as your protocol is text based, it should be able to see something happening.

Do you have more than one machine on your local network?

[Zaap]

Even telnet isn't working (public AND local address aswell).
My protocol is indeed text-based.

I'm working on my professional network so yes there are several computers in local (10-20).

[Zaap]

It seems to work now (and I don't know why).

The only modification I made was about my key generator (to encrypt the conversation) so I have no idea of the problem. Let see if it happens in the futur.

Thanks for help.

NB : It's strange because the connection seems a bit random. Sometimes I can't connect on my public address, and after few retries, it suddenly works.

[salem c]

If you're not already doing so - source control.
https://en.wikipedia.org/wiki/List_of_version-control_software

If you've got something that works, then make a commit.

> I already disabled firewall and I did a port forwarding on 9696 (my server port).
> I'm working on my professional network so yes there are several computers in local (10-20).
Is that the firewall on your machine, or the perimeter firewall between your LAN and the internet?

How is DHCP set up for your LAN?
Do your machines get static addresses with nice long lease times?

Is your perimeter firewall/router doing something weird with packets if it detects that the public IP address being requested is in fact your own public address.
It seems odd that canyouseeme works all the time.

Try running wireshark on your machine, and set it up to watch for any traffic on port 9696.
Wireshark can sniff all the packets on the local LAN, so you should be able to see if the messages are there, but maybe routed to the wrong local machine.

[Zaap]

Yes my IP is set to static. I'll see tomorrow what happen exactly with wireshark.

Edit : No way to reproduce the bug so I can't test with wireshark. I hope it's fixed now.