Port Forwarding with router DIR825AC

Hello forumers! I might need help, with my project. Making this arduino project for school. I know little things about arduino and so on, but know very few things about Internet communication. So I want make my own Blynk server and use Blynk app for my project, because that is so easy and professional way to present my project. Problem is with port forwarding, which in my case is little complicated. I want send data to my server where ever I am and need access to it via app. I use D-link router DIR825AC which has port forwarding as virtual server window. Other similar routers have port forwarding under advanced settings, which it does not. http://www.tomshardware.co.uk/answers/id-3230416/urgent-port-forwarding-virtual-servers-doesnt-work.html u can see same problem here.

I have tried differe sent ways to connect to my server and open different ports, but I think I doesnot understand that thing and I am confused. I have tried to connect with app over mobile network. When server is running, I can perfectly connect to admin page and so on: Also I am very beginner so be patient :smiley: and may even need direct instructions, how to do it, sorry.
Any help is appreciated! Thank You!

Information I found: Blynk server has 3 ports open for different security levels.

8441 - SSL/TLS connection for the hardware
80 - plain TCP connection for the hardware (no security)
443 - SSL/TLS connection for the Mobile Apps
8080 - plain TCP connection for hardware on the Local Server (no security)
9443 - SSL/TLS connection for the Mobile Apps on the Local Server

Port forwarding is not Blynk specific… you can Google your router model and the words port forwarding

I still dont have any idea, but I think I can just keep trying. But off topic, I got facinated that Blynk team has solved, something very intresting, infact sending Arduino data over USB without Internet shield to app. So I thought if there is anyway to do it, to send that data to your local server or even over Internet. I even googled it how to do it without blynk and some said, its impossible :joy: Blynk gave some another server file with that sending data over USB and if I make some slight changes in code, can I use that same way as blynk-cloud? I mean, does it work?

Now this, unlike Port forwarding, IS Blynk related :stuck_out_tongue:

Yes, that USB-Link simply turns your PC into an oversized Serial to Ethernet adapter :wink: and will work with Local Server as well.

I use these settings on one of my UNO’s The IP is for my Local Server inside my network… I can use port forwarding to connect to that Server from away from home.

NOTE the correct port to use is 8080

@echo off
setlocal EnableDelayedExpansion

REM === Edit these lines to match your need ===

set COMM_BAUD=9600
set SERV_PORT=8080

REM === Edit lines below only if absolutely sure what you're doing ===

Thanks! I will try this in the morning :D. So you opened port 8080 and public ip is My router wants public and private ports seperately :wink: and is not satisfied with only one port, but wants range of ports. Also off topic question. I read that I have two ip-s one is local like and public is So I must use public IP as remote ip? Stupid questions anyway. But teachers used to say that there is no stupid questions, but answers :rofl:

NO. Port 8080 is for the devices (the script) only to connect to the Local Server… of which it’s IP is on the Private side.

For port forwarding (which is not required with the USB link) you would redirect the App’s port (9443) from your router’s public IP (whatever your router gets from your IT service) to your Local Servers Private IP.


I think this tutorial needs a serious update on how to access local server from outside your local network: with step-by-step instructions on what/where and why, with screenshots/pics, things to be aware of (like ISP’s abilities to close certain 'protocols/ports)… i just started figuring out how github works, so please tell me if i can be a part of the update? I could draw a nice picture of the entire chain of network devices, used in the process for instance…

I’m also trying to connect to my local server.
My external IP is dynamic, and I have done the following:

  1. created an account on www.noip.com , and used it in Blynk app
  2. installed and launched DUC (Dynamic Update Client) on my RPi
  3. Redirected port TCP 80 (since my connection isnt ssl, right?) to local 9443 (this port works fine on local network)

    Not sure if i need to specify port range. If yes, then what is this range for non-ssl connection?
    The app keeps on telling me that ‘You don’t have internet connection’…
    So , i tried to check ports with www.PortCheckTool.com On both mobile and cable ISP it always responds with «Problem! I could not see your service on xxx.xxx.xxx.xxx on port (80). Reason: Connection timed out.» A footnote on the same page says that many ISPs close port 80 to stop viruses such as Nimda…

My mobile ISP support says they never block any ports at all, but somehow i suspect they think that im asking if they block certain IPs (some - by the Supreme court decision) - a very painful topic for Russia these days… This ‘blocking inferno’ is the reason why i had to switch to local server. Blink cloud, along with millions of other Google and Amazon IPs, was blocked in Russia by mistake, while hunting for Telegram IPs. Telegram works fine, btw…

My cable ISP says that for connections using internal IPs it doesn’t block ports, except SMTP (port 25), SMB (ports 137–139, 445)
DNS-requests on such connections are allowed only to DNS servers of «АКАDО Telecom»:

With all my useless attempts of port forwarding, and ISPs doing whatever authorities tell the to do, i really dont know where to direct my google-digging abilities… what do i have to read/watch on youtube to understand the whole picture? Maybe nothing will help until i pay for a VPN that i could set up and use right on my router?
How do i find out if my mobile/cable ISPs actually close ports? Any online tools? `Can i use other external ports (which ones?) and noip.com account to access my local server without an external static IP or by other means?
I’d like to access my local server from the outside at least on unsecured connection ports. I’ll figure out the automatic Let’s Encrypt certificate later.
Thank you!

According to https://2ip.ru/check-port/
ALL ports (80, 8080, 8443, 443, 8441-8444, 9443) listed in Blynk’s documentation are closed by my cable internet provider. Just checked 80 and 9443 on mobile phone - closed as well…
Does this site also lie because right there, below the results of check-port, they offer to ‘open any port’ by using hidemy.name VPN?
how do i find open ports in this mess?

How is this possible? These ports are standards for HTTP and HTTPS protocols. You can’t access web with those ports closed.

I might be wrong, but I think, that your ISP use double NAT or something similar. The public/private and dynamic/static IP adress are not the same thing. You said, that you have dynamic IP, so you used no-ip, that is fine. But if you have private IP address, you will not be able to connect to your PI on LAN from outside. Also, i do not recomend you to use ports like 20, 21, 25, 80, 81, etc… Because these ports are more likely to be blocked by ISP because botnets attacks to everything with opened common ports. At least by my own experiences. So, find out, wich type of IP you have. Then, try port froward to eg. not 80 but 5123, or something simillar random 4 number


yeah, i know!
that’s why i asked if this little bugger lies…
Any ideas where to find a reliable port-checker?

Thank you!
I just checked port 80 on 2ip.ru port-checker with enabled Free Browsec VPN Chrome add-in. Port is closed… I dont particularly trust 2ip.ru, since it tells me that all ports (that i need) are closed…
Maybe they’re all closed because i have private (internal) IP that may or may not (according to the ISP support) change, when i restart my router, and 2ip.ru shows the correct info on my closed ports?.. So, VPN, at least the free add-on kind, do not open ports? Do paid ones change anything, or signing up for public IP is the best?


so, i had the same problem, and it caused, that i could not access any kind of server running on my LAN. Nevertheless that i tried more routers and tons of settings including any kinds of port forwarding and virtual servers and stuff like that. NONE OF THEM never worked for me, i had still closed every port. So i decided, that i have to move on. You can try either request your ISP to have public IP address, and not to be behind any NAT, OR you can do wich i do, what is… (Wich i recomend you) Pay for a virtual server (VPS - Virtual Private Server). It was not fully free method wich i was looking for, but since that, my Blynk server is running without any fail for 1,20 € per month. As i said, it is not free, but you will be free from your troubles (at least in closed ports category). Also… there is a third way… look for the service named “ngrok” it allows you have ONE port of your pi accessible from the internet. I used it before, but since every time you reconnect your pi (or reboot or whatever) the number in ngrok connection URL will randomly changes, wich is very annoyng ( and also it is the tax for the “free” i think), anyway IDK how reliable is this service. If you pay for VPS, feel free to contact me, as i can help you with setup.
Good Luck!

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Closed for incoming traffic, not outgoing! :wink:

I normally recomend these sites:

http://www.whatsmyip.org (also has a port scanner)
https://portforward.com/ (many guides for many routers and scenarios)


What is the name of your VPS? Can it be used right on the router? My router supports VPN port forwarding, depending on device and/or software, so id like to set up my IoT devices to use VPN right on the router

http://www.whatsmyip.org1 (also has a port scanner)
https://portforward.com/1 (many guides for many routers and scenarios)

First one always gives me this

Second one doesnt have port scanners for Mac OS…

I think, I don’t fully understood your post, but it looks to me, that, you are don’t know difference between VPS and VPN. VPN has nothing to do with VPS. IDK if you can run VPS on your router, but most likely not. VPS - that what I pay for is basically some high power server on wich is running a lot of virtual machines wich emulates servers. VPN on the other hand, let you create secured tunnel from your network to another network e.g. from home LAN to your work. My VPS service provider is www.forpsicloud.sk, but I recommend you search for one that is in your country, if you say that is some telegram hunting going on… Also, some providers let you try for free first month, or so…

Do you have any good VPN to suggest us? Thanks


No, i do not, because i am not using it.


You may not need to do that. New routers have that option built in. I’m using it on my home/work routers and work fine.