MessagePasserTask JSON

MessagePasserTask Application

Overview

MessagePasserTask is a NetBurner embedded application that demonstrates JSON-based client-server communication. The application periodically sends status information to a web server via HTTP POST requests and processes the server's responses to control local hardware.

Purpose

This application serves as an example of how to:

• Implement web client functionality on embedded NetBurner devices
• Send and receive JSON data over HTTP
• Integrate hardware I/O (switches and LEDs) with network communication
• Handle server responses and error conditions

Key Features

Network Communication

• Makes HTTP POST requests to a configurable server endpoint
• Sends JSON data containing device status information
• Processes JSON responses from the server
• Includes comprehensive error handling for network operations

Hardware Integration

• Reads DIP switch positions to monitor user input
• Controls LEDs based on server responses
• Automatically triggers network requests when switch positions change

Data Exchange

The application sends the following information to the server:

• Device MAC address (as DEVICEID)
• System uptime in seconds
• Current timestamp message
• Student name identifier
• Current switch position values

The server responds with:

• Success flag indicating message processing status
• Current switch value for LED control
• Response message for display

Configuration

Server URL

The target server URL is configurable via the Url config object:

static config_string Url(appdata, "http://class.netburner.com/post/", "MessageUrl");

Student Identity

Update the student name before deployment:

const char *StudentName = "Attendee Name";

Application Flow

1. Initialization
   • Initialize NetBurner system and network stack
   • Wait for active network connection (DHCP)
   • Display IP address information
   • Start web client task
2. Main Loop
   • Monitor DIP switch positions
   • Trigger network request when switches change
   • Send periodic status updates every 10 seconds
3. Network Request Process
   • Build JSON object with current status
   • Send HTTP POST to configured server
   • Parse JSON response
   • Update LEDs based on server response
   • Display status messages

Error Handling

The application includes robust error handling:

• Network connection timeouts (10 second limit)
• JSON parsing errors
• Server response validation
• Hardware I/O error recovery

Error states are logged to the console with descriptive messages using the HandleErrorState() function.

Hardware Requirements

• NetBurner development board with network capability
• DIP switches for input
• LEDs for status output
• Network connection (Ethernet)

Build Dependencies

Required NetBurner libraries:

• init.h - System initialization
• webclient/web_client.h - HTTP client functionality
• json_lexer.h - JSON parsing and generation
• config_obj.h - Configuration management
• ipshow.h - Network diagnostics
• utils.h - Hardware I/O utilities

Usage Notes

• The application automatically starts network communication after initialization
• LED patterns indicate server response status
• Switch changes immediately trigger new server requests
• Console output provides detailed operation logging
• System diagnostics are enabled for debugging (should be disabled in production)

Troubleshooting

Common issues and solutions:

• Network timeouts: Check server availability and network connection
• JSON parsing errors: Verify server response format matches expected structure
• LED not responding: Check server CURSWITCH value in response
• No SUCCESS flag: Server may be rejecting the request format

Enable HTTP diagnostics for detailed network troubleshooting:

SetHttpDiag(true);

Development Notes

This application demonstrates best practices for NetBurner embedded web clients and can serve as a foundation for more complex IoT communication scenarios.