Android POS Development (Simple Printing App)

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Looking for Android Developer to Build a Lightweight POS App (Kotlin Preferred, No Vendor SDKs) I'm looking for a skilled Android developer (Kotlin-native preferred) to build a focused POS companion app with the following strict requirements: Functional Requirements Periodic Polling: App must poll a configurable HTTPS URL at a user-defined frequency (e.g., every X seconds). The polling request must send a JSON payload containing: Device MAC address Device serial number A user-defined third identifier (settable in settings) Triggering a Print Job: If the server responds with HTTP 210, the app should: Get the bitmap from the JSON response (it will be base64 encoded) Convert the image to raster ESC/POS format Send raw ESC/POS raster image commands directly to the internal printer (no SDKs) After print, respond back to the original server with a JSON payload indicating success/completion or error if any, including all 3 identifiers again ESC/POS Printer Control: The app must communicate with the internal printer using raw ESC/POS commands only so as to be compatible with a wide range of POS devices Absolutely no use of vendor SDKs (e.g., no Sunmi, Epson, etc. SDKs) Image must be formatted and sent using the ESC * or GS v 0 raster command directly over whatever low-level interface is available (e.g., file descriptor, USB, or serial) Settings Page: Must allow the user to: Set the server polling URL (there will be a default) Enter a custom third identifier (free-form text) Set the polling interval (in milliseconds) Select and test the printer connection by printing a test bitmap or text Persist these settings locally Technical Constraints & Preferences Must be written in Kotlin (or Kotlin + minimal Java) App must not rely on any vendor SDKs Must support direct communication with internal printer hardware App should be suitable for headless or kiosk deployments and run in the background unless the settings page is triggered (by re-opening the app) All HTTP calls must be HTTPS, JSON-based, and support graceful error handling Must work without Google Play Services Ideal Developer Profile Proven experience building Android apps that interface with hardware Comfortable working with ESC/POS command sets, raw byte protocols Familiar with Android's permission model, background services, and battery optimizations Able to deliver production-grade, minimal UI apps focused on reliability and performance If you’re confident working close to the hardware and building apps without third-party SDKs, please reach out with: Your experience with similar projects Estimated delivery timeline Clarifying questions, if any.

Keyword: Java