TCP Server

Simple TCP Server Example

A NetBurner embedded TCP server application that creates a listening socket on port 23 (Telnet) and accepts client connections for communication.

Overview

This application demonstrates how to implement a basic TCP server on NetBurner hardware. The server listens for incoming connections and provides a simple echo-style communication interface where it receives data from clients and displays it locally.

Features

• TCP Server: Creates a listening socket on port 23 (standard Telnet port)
• Client Connection Handling: Accepts incoming TCP connections from clients
• Data Reception: Reads data from connected clients using a simple read() function
• Connection Management: Handles client disconnections gracefully
• Multi-tasking: Uses RTOS tasks for concurrent operation

Technical Details

Configuration

• Listen Port: 23 (Telnet)
• Receive Buffer Size: 4096 bytes
• Maximum Pending Connections: 5
• Task Priority: MAIN_PRIO - 1 (higher than UserMain)

Key Components

TcpServerTask

The main server task that:

1. Creates a listening socket bound to INADDR_ANY on the specified port
2. Waits for client connections using accept()
3. Sends welcome messages to connected clients
4. Continuously reads data from clients until disconnection
5. Closes connections and waits for new ones

Buffer Management

• Uses a global receive buffer (RXBuffer) of 4096 bytes
• Null-terminates received data for string processing
• Displays received data length and content via iprintf()

Usage

Testing with Telnet

To test the TCP server, use a Telnet client from any system on the same network:

telnet <netburner_ip_address>

Where <netburner_ip_address> is the IP address of your NetBurner device.

Expected Behavior

1. The server displays "Waiting for connection on port 23..."
2. When a client connects, it shows the client's IP address
3. The client receives welcome messages:
   • "Welcome to the NetBurner TCP Server"
   • Connection details with server IP and port
4. Any data sent by the client is echoed to the server console
5. When the client disconnects, the server closes the connection and waits for new ones

Implementation Notes

Connection Lifecycle

• The server uses a blocking accept() call to wait for connections
• Each client connection is handled sequentially (single client at a time)
• The read() function blocks until data is received or connection closes
• Connection closure is detected when read() returns 0 or negative value

Limitations

• Single Client: This example handles one client connection at a time
• Sequential Processing: New connections must wait until the current client disconnects
• No Timeout: Connections remain open indefinitely until client closes

For Multiple Clients

This example uses a simple read() approach for single client connections. For handling multiple simultaneous client connections, refer to the "TCP Multi Socket Server" example.

System Requirements

• NetBurner hardware platform
• NetBurner RTOS (NBRTOS)
• Network connectivity (Ethernet)
• Telnet client for testing

Troubleshooting

Common Issues

1. Connection Refused: Verify the NetBurner device IP address and network connectivity
2. Port Already in Use: Ensure no other service is using port 23
3. No Response: Check if the TCP server task started successfully

Debug Output

The application provides console output for:

• Server startup and port binding
• Client connection events with IP addresses
• Received data content and byte counts
• Connection closure events

Code Structure

main.cpp
 TcpServerTask()     - Main TCP server loop
    listen()        - Create listening socket
    accept()        - Accept client connections
    read()          - Receive client data
    close()         - Close connections
 UserMain()          - Application initialization
    init()          - System initialization
    OSTaskCreate()  - Create server task

Related Examples

For more advanced TCP server implementations, see:

• TCP Multi Socket Server - Handles multiple simultaneous client connections