Protocolo

This is a layered communication protocol (similar to the OSI model) implemented for a university project (4th semester Computer Engineering at Insper). It provides reliable file and object transfer over serial ports using:

Key Components

1. Codec class - Handles packet encoding/decoding with:

   • Start/end delimiters: #StR# and #eNd#
   • CRC-16 error detection
   • Header with metadata (type, packet ID, payload size, info field)
   • Support for multiple data types (int, bytes, string, Python objects via pickle)
   • Maximum payload size of 255 bytes

2. Enlace class - Link layer that manages:

   • Serial port communication (115200 baud rate)
   • Request/accept handshake mechanism
   • File transfer with automatic chunking
   • Object serialization and transmission
   • Automatic retransmission on errors
   • Asynchronous packet reading via threading
   • Logging of all transmissions

Protocol Message Types

• Type 0: Request to send (object/file)
• Type 1: Accept request
• Type 2: Object data
• Type 3: Start of file data
• Type 4: File data chunk
• Type 5: Data confirmation/ACK
• Type 6: End of file data
• Type 7: Error message

Features

• Request-response pattern: Sender requests permission, receiver accepts
• Reliable delivery: CRC checks, ACKs, automatic retransmission
• File chunking: Large files split into 255-byte packets
• Flow control: Sequential packet numbering with confirmations
• Error handling: CRC validation, timeout detection, packet reordering
• Logging: Comprehensive transmission logs with timestamps

This protocol implements a reliable data transfer mechanism suitable for educational purposes, demonstrating concepts like framing, error detection, flow control, and session management.