SRS: System Requirements Specification - TINF20C/Team_4_Websockets-lwIP GitHub Wiki
- 1. Goal
- 2. Use Case
- 3. Non-functional Requirements
- 3. Functional Requirements
- 4. Bug Fixes
- 5. Product data
- 6. Enhancements
- 7. References
| Version | Date | Author | Comment |
|---|---|---|---|
| 0.1 | 26.10.2021 | Maximilian Meier | created |
| 1.0 | 8.11.2021 | Maximilian Meier | Release Version |
The goal of this project is to address the architectural deficiencies of patch "#9525 (httpd: add websocket support)"[1] in coordination with the project community. This experimental base is to be improved and brought through the approval process in the open-source project.
Furthermore, a demo server is to be designed and implemented in a virtual environment under Windows.
For demonstration and testing purposes of the features, a GUI-based test client shall be designed and implemented.
For development and testing purposes the newest version of lwIP must be installed and made to run on a windows system, due to a lack of embedded systems at our disposal to run it on. From there the Patch #9525 must be implemented with lwIP on a Windows system before the architectural deficiencies can be addressed. To make sure that lwIP and its patch #9525 still work afterwards, several tests are supposed be designed to ensure working order.
| Related Business Process: | Prozess-ID: UC01 |
|---|---|
| Use Cases Objective: | Customer is developing a CPU and wants to ensure support for TCP/IP and Websockets. |
| System Boundary: | lwIP allows the hardware to use TCP/IP. |
| Precondition: | The user can find and download lwIP via a conventional Internet browser. Setting up the software is adequately documented, and users can do it themselves. |
| Postcondition on success: | lwIP is executable on the CPU of the user. |
| Involved Users: | Role name: CPU developer |
| Triggering Event: | Developer gets the order, has own ambitions to extend the CPU with TCP/IP functionalities. |
| Related Business Process: | Prozess-ID: UC02 |
|---|---|
| Use Cases Objective: | Customer works with microcontrollers (e.g. ESP8266) as a hobby and wants to build a TCP/IP stack on top of it. |
| System Boundary: | lwIP allows the hardware to use TCP/IP. |
| Precondition: | The user can find and download lwIP via a conventional Internet browser. Setting up the software is adequately documented, and users can do it themselves. |
| Postcondition on success: | lwIP is executable on the user's microcontroller. |
| Involved Users: | Role name: Hobby developer |
| Triggering Event: | Developer gets the order, has own ambitions to extend the microcontroller with TCP/IP functionalities. |
lwIP primary focus is on a compact architecture that enables it to run on small embedded systems. If the project is to go through the approval process to become part of the main product, compact code will improve chances for approval.
For lwIP to run on systems with small processing power the code must be efficient. Efficient Code writing may improve our chances to get through the approval process.
The GUI for the Test-Client should be intuitive to use for any user to test the WebSockets functionality. The GUI should also be designed to be as accessible as possible and convey as much relevant information as necessary.
If all architectural problems with patch #9525 can be resolved, we will submit our changes for approval to the maintainer of lwIP. It is however not guaranteed that the maintainer even has time to look at our submissions.
At the end of the project, it should be possible to use lwIP with patch #9525 as an easy to execute Program to simplify grading.
The code for base64 encoding should become its own function. This is due to the fact that it is used multiple times throughout the Project and implementing it each time is unnecessary and space consuming for a Program specifically designed to be light weight. Or in other words it is supposed to take up as little space and processing power as possible[1].
This is the main goal of patch #9525, to enable to usage of websockets. At the end of this project, it should be possible to exchange data through lwIP using websockets. Websockets enable bidirectional connections and keep the connection between server and client open, thus the server can send data without it being specifically requested by the client.
For demonstration and testing purposes a test client shall be designed and build.
A http webserver may have to be implemented to enable testing of WebSocket functions and behaviour.
From a hardware point of view lwIP requires no more than tens of kilobytes of free RAM and roughly 40 kilobytes of code ROM[2]. It's small size and memory usage is the main feature of the software and code must be written accordingly to ensure this remains true.
/BUG10/Refactoring of lwIP base64 function for usage in the websocket patch
/BUG20/Opening a websocket connection inevitably leads to a "Run-Time Check Failure #2
/BUG30/Any Executable would only be usable for the specific device and network it was designed for
/BUG40/Inconsistent length of the JSON object to be returned
| [1] | „lwIP - A Lightweight TCP/IP stack - Patches: patch #9525, httpd: add Websocket support [Savannah]," [Online]. Available: https://savannah.nognu.org/patch/?9525. [accessed 15.10.21]. |
|---|---|
| [2] | „lwIP wiki,“ [Online]. Available: https://lwip.fandom.com/wiki/LwIP_Wiki. [Zugriff am 07.11.2021]. |