Main Components

1. SMS Service Layer

Implements the core business logic for SMS submission through a multi-step validation and processing pipeline.

• Validation Steps: Validates ESME ID, application existence, ESME connectivity, and transaction UUID
• Contact Policy Checks: Applies blacklist validation and registration filter checks
• Message Submission: Routes approved messages through the SMPP gateway
• Journal Recording: Records all submission attempts together with message statistics
• Monitoring: Captures metrics for each processing step, including success/failure rates and execution timing

2. SMPP Infrastructure

Manages SMPP connectivity, session lifecycle, and message transmission.

• Multiple ESME Support: Supports concurrent operation of multiple SMPP client connections
• Connection Management: Handles bind/unbind operations, connection state monitoring, and automatic reconnection
• Message Processing Strategies:
  • Single-part messages using standard submission
  • Multi-part messages using UDH concatenation
  • Payload mode using TLV field transmission
• Encoding Support: Supports GSM7 (DefaultType), Latin-1, and UCS-2 (Unicode) encodings
• Rate Limiting: Provides configurable per-ESME throughput control as a planned feature

3. Statistics & Journaling

Tracks message lifecycle events and persists operational records.

• In-Memory Cache: Uses a TTL-based cache for active message sessions
• Journal System: Implements asynchronous file-based logging with rotation and export support
• State Tracking: Stores message lifecycle states such as scheduled, submitted, delivered, and failed
• Export to S3: Automatically exports journal files to external object storage

4. SMPP Listener

Processes incoming SMPP PDUs, primarily delivery receipts.

• Delivery Reports: Handles deliver_sm messages containing delivery status updates
• Status Mapping: Maps SMPP delivery states to internal application states
• Binary Parsing: Extracts delivery metadata from TLV fields
• Statistics Updates: Updates message status in the statistics cache

5. Data Models

Defines the core domain entities used across the system.

• SMS Model: Represents the full SMS entity, including addressing and validation attributes
• Statistics Model: Extends SMS data with tracking fields such as errors and SMPP states
• Delivery Status: Parses and structures delivery receipt information
• Helper Methods: Provides utility methods such as address normalization and privacy-safe hashing

6. Validation Helper

Analyzes message payload characteristics before submission.

• Length Calculation: Calculates message length and required segment count
• Encoding Detection: Detects the character encoding required for transmission
• Part Estimation: Determines how many SMS parts are needed for delivery