UDP Notify Callback Function

UDP Notify Example

Overview

This application demonstrates how to use callback functions to handle incoming UDP packets in a NetBurner NNDK (NetBurner Network Development Kit) environment. The example implements an asynchronous UDP packet receiver that automatically processes incoming data through a registered callback function.

Application Details

Application Name:** UDP Notify Example
Listen Port:** 2121
Protocol:** UDP (User Datagram Protocol)

Key Features

• Callback-based UDP handling: Uses a notification callback function instead of polling
• Automatic packet processing: Incoming UDP packets trigger the callback function automatically
  
• Network stack initialization: Includes proper DHCP client setup and network interface management
• Packet validation: Validates received packets before processing
• Diagnostic support: Includes system diagnostics for debugging

How It Works

Network Initialization

1. Initializes the network stack
2. Enables system diagnostics
3. Waits for active network connection (5 second timeout)
4. Waits for DHCP address assignment to complete
5. Displays the listening IP address and port

UDP Packet Handling

1. Creates a FIFO (First-In-First-Out) buffer for incoming packets
2. Registers the UDP port with a callback function using RegisterUDPFifoWithNotify()
3. When packets arrive, the callback function UdpListenCallback() is automatically invoked
4. The callback processes the packet and displays information about the sender and data

Callback Function Behavior

The UdpListenCallback() function:

• Creates a UDPPacket object from the FIFO
• Validates the received packet
• Extracts packet size and source IP address
• Displays the packet data using ShowData()
• Handles invalid packets gracefully

Technical Components

Key Functions

• RegisterUDPFifoWithNotify(): Registers UDP port with callback notification
• UDPPacket: Class for handling UDP packet data
• OS_FIFO: Operating system FIFO for packet queuing
• WaitForActiveNetwork(): Waits for network connectivity
• GetInterfaceBlock(): Retrieves network interface information

Callback Function Signature

void UdpListenCallback(OS_FIFO *pfifo, uint16_t port)

The callback function must match the typedef:

typedef void (udp_data_notify)(OS_FIFO *pfifo, uint16_t port);

Usage

1. Compile and deploy the application to a NetBurner device
2. Connect the device to your network (DHCP will assign an IP address)
3. Monitor the console output to see the assigned IP address
4. Send UDP packets to the displayed IP address on port 2121
5. View the output as the callback function processes and displays received packets

Example Output

Application: UDP Notify Example
NNDK Revision: [version]
Listening for UDP packets on 192.168.1.100: 2121
 
UdpListenCallback()
Received a UDP packet with 15 bytes from : 192.168.1.50
[Packet data display]

Differences from Standard UDP Handling

This example uses callback-based notification rather than polling:

• Standard approach: Use RegisterUDPFifo() and manually check for data
• Notification approach: Use RegisterUDPFifoWithNotify() with automatic callback execution

Requirements

• NetBurner NNDK development environment
• NetBurner-compatible hardware device
• Network connection with DHCP server
• UDP client application for testing (can send packets to port 2121)

Notes

• The application runs in an infinite loop, continuously listening for UDP packets
• System diagnostics are enabled for development/debugging purposes
• Remove diagnostic features for production deployment
• The callback function executes in the context of the network stack
• Packet timeout can be configured by replacing the 0 parameter in UDPPacket constructor