TCP Client

TCP Client Example Application

Overview

This is a simple TCP client application built for NetBurner hardware that demonstrates how to create and use a TCP client connection. The application provides a web-based interface that allows users to send messages to any TCP server by specifying the destination IP address, port number, and message content.

Features

• Web-based Interface: Complete interaction through a web page interface
• Configurable Connection: Set destination IP address and port number
• Message Transmission: Send custom messages to TCP servers
• Auto-fill Functionality: Automatically fills in the requesting client's IP address as default destination
• Error Handling: Comprehensive error reporting and logging
• Real-time Feedback: Connection status and transmission results displayed

Application Structure

Core Files

• main.cpp: Main application entry point and initialization
• clientweb.cpp: Web interface implementation and TCP client functionality
• clientweb.h: Header file for web interface functions

Key Components

Main Application (main.cpp)

• Initializes the NetBurner system
• Enables system diagnostics
• Starts HTTP server for web interface
• Waits for active network connection
• Displays IP addresses
• Runs main application loop

Web Interface (clientweb.cpp)

• Implements web page form handling
• Processes POST variables from web form
• Manages TCP client connections
• Handles message transmission
• Provides real-time status feedback

How It Works

1. Initialization: The application starts up, initializes the network, and launches the HTTP server
2. Web Interface: Users access the web page which displays form fields for:
   • Destination IP address (auto-filled with requesting client's IP)
   • Destination port number (defaults to 2000)
   • Message content
3. Message Transmission: When the form is submitted:
   • A TCP connection is established to the specified server
   • The message is transmitted
   • Connection status and results are logged
   • The connection is closed
4. Response: The web page redirects back to the main interface

Configuration

Default Settings

• Default Port: 2000
• Connection Timeout: 5 seconds
• Maximum Message Size: 1024 characters

Web Form Fields

• tfDestIpAddr: Destination IP address field
• tfDestPortNum: Destination port number field
  
• tfMessage: Message content field
• SendMessage: Submit button trigger

Usage Instructions

1. Setup: Deploy the application to NetBurner hardware
2. Network: Ensure the device is connected to your network
3. Access: Open a web browser and navigate to the device's IP address
4. Configure:
   • Enter the destination TCP server IP address
   • Set the destination port number
   • Type your message
5. Send: Click the submit button to transmit the message
6. Monitor: Check the console output (MTTTY) for connection status and errors

Testing

TCP Server Requirement

A TCP server must be running and listening on the specified IP address and port before sending messages.

Included Test Server

NetBurner provides a Windows-based TCP server for testing:

• Location: \nburn\pctools\TCP\TcpServerWin
• Includes: Executable and source code
• Purpose: Simple TCP server for testing client connections

Technical Details

Network Functions Used

• connect(): Establishes TCP connection with timeout
• write(): Sends data over TCP connection
• close(): Closes TCP connection
• GetSocketRemoteAddr(): Gets client IP address

Error Handling

• Connection failure detection and reporting
• Invalid parameter validation
• Timeout handling
• Detailed error logging to console

Memory Management

• Static buffers for message storage
• Automatic cleanup on connection close
• Bounds checking for message size

Troubleshooting

Common Issues

1. Connection Failed: Ensure TCP server is running and accessible
2. Network Not Ready: Wait for network initialization to complete
3. Invalid IP Address: Verify IP address format and reachability
4. Port Conflicts: Ensure destination port is not blocked or in use

Debug Output

All debug information is sent to stdout and can be viewed using MTTTY terminal application.