Introduction
TextNet Browser APK is an Android app that allows anyone to browse the web without a mobile data connection! SMS is used as a medium for transmitting HTTP requests, where pre-parsed HTML responses are compressed with Google's Brotli compression algorithm and encoded using Base-114 (based on Basest).
Furthermore, users can act as servers at the press of a button using their primary phone number and their own Wi-Fi/data connection, allowing peer-to-peer networking.
How it works (the client)
The app uses a permission that allows a broadcast receiver to receive and parse SMS messages without requiring the app to be registered as the default messaging app. SMS permissions present a security concern, but the code for this app is open source and all internet permissions are partitioned to the server module. This prevents the application from generating internet traffic unless it is configured as a server. Additionally, SMS messages can only be sent to and received from a registered server number as the client. The app communicates with a "server phone number", which is a phone number controlled by a "server host" that communicates directly over SMS with Android's SMS APIs. To send URL requests to the server, the encoded data is encoded in custom base 114. It usually only takes one SMS to complete the order, but just in case, each message is prepended with the order number. In response to a request, the server uses an Android WebView component to simulate a regular website request in order to avoid the restrictions that some services (such as Cloudflare) place on HTTP clients. The HTML can also be dynamically loaded if necessary using Javascript, allowing any content on the website to be processed by the script. In the event that only HTML is transferred back to the recipient device, the page will not load again. A HTML document is stripped of unnecessary tags and attributes, compressed into raw bytes, and then encoded. The messages are encoded into 160 character segments (maximizing the GSM-7 standard SMS size) and sent to the client app for parsing and displaying.
A side note: Brotli's compression savings have been estimated to be around 20% on average, but often they can be much higher! The website example.com is 285 characters in stripped HTML, but only 2 SMS messages (189 characters) are needed to receive it. There is still a 225% efficiency gain despite the overhead in data transmission!
What is the purpose of encoding HTML?
SMS was developed in 1984 to utilize the extra bytes from phone data channels. It was originally designed to support only 128 characters in a 7-bit alphabet. For the purpose of supporting a subset of the UTF-8 character set, a new standard called UCS-2 was created. While still limited by 160 bytes, UCS-2 supports more characters (many of which can be seen in HTML documents) but only allows 70 characters per SMS. In comparison to sending raw HTML over SMS, more data can be sent per SMS message by encoding all data in GSM-7. It may be even more efficient to create an encoding system that uses all the characters in UCS-2, but this limits compatibility and is beyond the scope of the project.
Hosting of servers
The TxtNet Browser has been rewritten to include a server hosting option. In place of the now-deprecated Python server, any user can now act as a server host, allowing distributed communication.
The background service can be enabled by tapping on the overflow menu and selecting "TxtNet Server Hosting". To initialize a background service, press the "Start Service" toggle once the necessary permissions have been granted.
The TxtNet Server uses the primary mobile number associated with your active carrier subscription SIM card as the number that others can add and connect to.
It is important to note that this feature is still in its infancy and is likely to have many issues in the future. If you encounter any problems, please submit an issue report.
Benefits and Impact
TextNet Browser has the potential to bridge the digital divide by providing internet access to individuals who would otherwise not connect. This app opens up a world of opportunities for people in remote areas. It enables them to access educational resources, communicate with others, and stay informed about global events. With TextNet Browser, users can browse websites, read articles, check emails, and perform various online tasks, all without a mobile data plan.
Conclusion
TextNet Browser APK is a game-changer in internet accessibility. By leveraging SMS, Brotli compression, and a custom encoding format, this Android app enables users to browse the web without a mobile data connection. Whether in remote areas or regions with limited connectivity, TextNet Browser empowers individuals to access the vast resources and opportunities available online. With its innovative approach, TextNet Browser has the potential to bridge the digital divide and make the internet more accessible to people around the world.
