Port forwarding issue

I have a working local blynk server:)
I have also port forwarded 9443 and 8080 and checked them working fine on
But the app won’t connect to the server when I use mobile data(outside home)

This image is what i keep on seeing indefinitely…
Any suggestions to overcome this?

Are you sure you have forwarding 9443 to IP local server ?
check the local IP server, is it a static IP ?
Try to forward 443 and connect blynk to 443 intead of 9443
I use that port , not 9443

Yes, the local IP Server is static

How do i check this?!

To do this, i only have to change to port 443 from 9443 during login right??

  1. Im still not able to use local server using mobile data after considering points (!) and (3)

yes, forward 443 port on your router and connect to 443 w/ blynk app

I’m still facing problem in accessing local server from outside home…
I did the following, please tell where i’m going wrong :

  1. created a local server, works perfectly at home
    2)forwarded port 9443,8080,443 on router, and 9443 says ‘open’ on
  2. when i try to login using custom settings on port 9443, local server, outside home network, the loading window(three green dots) would show endlessly

What IP address are you using in your custom server settings screen?
Do you have a static external IP address, or are you using a DDNS service?


As @PeteKnight said, you have to know if you have a static IP address, or you just have a dynamically allocated IP address from ISP.
I’ll explain the steps more clearly for each scenario:

A) Dynamically Allocated IP Address from ISP

  1. If you have dynamically allocated IP address (normally, more than 99%), e.g. 45.45.a.b, and your local server is in local network @
  2. Forward all ports 9443, 8080, 443 to your local Blynk Server @
  3. Get a free DDNS service at,, etc… For example you get a DDNS account You can try if it’s working by pointing your WebBrower to

to access your Local Blynk Server admin page.

  1. In your phone/tablet APP, select server : and port: 9443 instead of your local server IP This will work no matter if you’re using inside or outside network.

If it’s working, you certainly have to follow several more steps to ensure is always automatically updated with correct dynamically-allocated IP address whenever your ISP assigns a new IP address (router reboot, etc…).

B) Statically Allocated IP Address from ISP, e.g. 45.45.a.b

  1. You just need to forward all ports 9443, 8080, 443 to your local Blynk Server @
  2. In your phone/tablet APP, select server : 45.45.a.b and port: 9443 instead of your local server IP This will work no matter if you’re using inside or outside network
  3. It’s always better to use DDNS, just in case something happens, and especially you don’t need to remember complicated IP Address 45.45.a.b, but just

In some special case, ISP uses a double NAT, then you have no way to reach your server from outside, unless you deal with ISP to change (and pay some more). Do a search on double NAT in this forum if necessary.

I was using my computer’s local ip address until now, but now I’m using ddns service, as said by @khoih and it works perfectly… Thank you so much for the support!

Thankyou so much…I’m really happy this worked after weeks of trying…this wasn’t possible without your guidance @khoih
Thanks again!

Just so that you’re aware for the future, your local IP address isn’t visible outside of your network. There must be hundreds of millions of routers that sit at on a local network, but that doesn’t mean that you can access them external on that IP address.

It’s the public (WAN) IP address that needs to be used, and the router needs to be configured to send the appropriate traffic to your internal device (your Blynk server in this case). That’s what the port forwarding does.

If your public IP address changes from time to time then you need to use a DDNS service to route traffic to the current public IP address for your network. For this to work, you need to have an update client running on your network that keeps the DDNS service updated with your current IP address whenever it changes.


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To know your Public IP, just go to
You can see your public IP and scan port

Thanks for the information and all the support! :smile:

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