TCP Server Using Via

TCP Server Via Example

Overview

This application demonstrates a TCP server implementation for multi-interface NetBurner devices using the listenvia() function. The server creates multiple listening sockets - one that listens on all network interfaces and additional sockets that listen on specific network interfaces.

Features

• Multi-Interface Support: Creates listening sockets for each available network interface
• Multiple Concurrent Connections: Supports up to 10 simultaneous TCP connections
• Port Management: Uses incrementing port numbers starting from port 23
• Single-Task Architecture: Uses select() to handle multiple sockets within one task
• Connection Monitoring: Provides detailed logging of connections and interface information

Technical Details

Configuration

• Base Port: 23 (Telnet)
• Maximum Connections: 10 concurrent connections
• Read Buffer Size: 1,024 bytes
• Connection Queue: Up to 5 pending connection requests per listening socket

Socket Architecture

The application creates the following listening sockets:

1. One socket listening on all interfaces (port 23)
2. For each available network interface:
   • One socket on port 24 (listenPort + 1)
   • One socket on port 24 + interface_number

Network Interface Handling

• Automatically detects available network interfaces using GetInterfaceBlock()
• Creates dedicated listening sockets for each interface using listenvia()
• Provides interface-specific connection information to clients

Usage

Building and Running

1. Compile the application for your NetBurner device
2. Deploy to the target hardware
3. The application will automatically start listening on configured ports

Testing Connections

Use Telnet to test connections from the command line:

telnet <ip_address> <port>

Examples:

• telnet 192.168.1.100 23 - Connect to the all-interfaces socket
• telnet 192.168.1.100 24 - Connect to interface 1, port 24
• telnet 192.168.1.100 25 - Connect to interface 1, port 25

Client Interaction

• Upon connection, clients receive a welcome message
• Interface information is displayed showing which interface accepted the connection
• Type 'Q' to quit and close the connection
• Server echoes received data and provides connection status

Code Structure

Main Components

Initialization**

• System diagnostics enabled
• Waits for active network (10-second timeout)

• Displays IP addresses for all interfaces

  Socket Management**

• listeners[] array stores all listening socket file descriptors
• fdArray[] manages active client connections

• Automatic socket recovery on errors

  Event Loop**

• Uses select() for efficient I/O multiplexing
• Processes new connections, data reception, and errors
• Automatic cleanup of closed connections

Key Functions Used

• listen() - Creates socket listening on all interfaces
• listenvia() - Creates socket listening on specific interface
• accept() - Accepts incoming connections
• select() - Monitors multiple sockets for I/O events
• TcpGetSocketInterface() - Retrieves interface information

Error Handling

• Connection Limit: When server is full, new connections are rejected with a message
• Socket Errors: Automatic detection and recovery of failed listening sockets
• Read Errors: Proper cleanup of corrupted client connections
• Interface Failures: Continues operation even if some interfaces fail

Application Output

The application provides detailed console output including:

• Network interface discovery and socket creation status
• Connection acceptance with client IP and port information
• Interface identification for each connection
• Data reception logging
• Connection closure notifications
• Error condition reporting

Requirements

• NetBurner hardware platform
• NetBurner SDK with TCP networking support
• Multi-interface network configuration (optional for full functionality)

Notes

• System diagnostics are enabled by default (should be disabled for production)
• Socket file descriptors are automatically managed and cleaned up
• The server continues running indefinitely until manually stopped