How does UDP mode 1 works?

Posted on October 7, 2020 @ 10:05 pm

In this article I will explain how UDP mode 1 works and why it sometimes disconnects after downloading an X amount of data.

UDP mode 1 was created to bypass a network restriction and is being used by users who want to get free internet.

If you are not using it for free internet then there is no point in using this UDP Mode 1. Its better to use a different protocol/mode.

If you are using DroidVPN for free internet this means that you have no data plan. And it is a fact that if you have no data plan you cannot browse the internet.

When you browse the internet, your device (eg: computer/cellphone) will send packets of data to the internet. All those data needs to pass through your ISP. Your ISP will check if you have a data plan. If you do not have a data plan, it will drop all your data packets. Which means you will have no internet connection.

While testing our ISP, I saw that you can still send some UDP packets using UDP mode 1 even if you do not have a data plan, the only problem is you can only send a limited number of packets per data connection. That limit is set by your ISP not us. Meaning once you enable your mobile data you can send and receive an X amount of packets. Since each ISP has a different set of limit the tcount(send) and rcount(receive) setting needs to be customized to the limit of your ISP. I will release a new tool soon to automatically find the correct tcount and rcount.

Like I have said there is a limit on a total number of packets you can send, so once you reach that limit, the VPN will disconnect. Reconnecting the vpn won't work because the limit is already reached. To reset the limit you need to disable/enable your mobile data. Doing that will reset the limit counter on your ISP. I also believe the limit counter has a time expiration which means if you do not disable/enable your connection it will eventually expire after an X amount of time. I do not know the exact time since each ISP probably has different expiration of those counters.

So to recap here is what happens when you use UDP mode 1.

In the example below, lets say your ISP has the limit counter set to 50.

  1. You enabled your mobile data and starts browsing using UDP mode 1
  2. All the data passes through your ISP and it increases limit counter for each data you send.
  3. As long as your limit counter is below 50 all data you send and receive will pass through your ISP. Meaning you will get internet access
  4. Once the limit is over 50 all data you send after that will be dropped by your ISP. Meaning no more internet connection and the VPN will disconnect
  5. You try to reconnect but since you are over the limit counter the reconnection requests wont reach our server. Sometimes the connection requests do reach our servers but you wont receive the reply of our servers. Meaning the VPN wont connect.
  6. You then disable and enable your mobile data. Doing that will reset the limit counters. Meaning the limit counters are now back to zero
  7. Connecting the VPN will now work since the limit counters is back to zero and now you are back to step 2
  8. Sometimes you will get the "user is online" error. That's because on step 5, our server receive your connection request but you did not receive the reply of the server. So what happens is the server thinks you are still connected. If the server do not receive any data after 60 seconds it will mark your account as offline again, which it will since you are not really connected. Note that UDP is connectionless so it doesn't really know if you are connected or not and has to rely on timeouts (eg: if you are still sending data or not)
And to clarify again the limit counter is set by your ISP and not us. There is no way to bypass that, well none that I know of.