Dual TCP To Serial

DualTCP2Serial Example

A NetBurner embedded application that bridges TCP network connections to serial ports, enabling remote access to serial devices over Ethernet.

Overview

This application creates TCP-to-serial bridges on two serial ports simultaneously, allowing network clients to communicate with serial devices as if they were directly connected. Each serial port listens on a different TCP port and handles one client connection at a time.

Features

• Dual Serial Port Support: Bridges both serial port 0 and serial port 1
• Bidirectional Data Transfer: Data flows seamlessly between TCP clients and serial devices
• Connection Override: New clients can override existing connections after a timeout period
• Configurable Parameters: Easily adjust baud rates, TCP ports, and timeout values
• Error Handling: Robust handling of network and serial port errors

Configuration

Default Settings

Parameter	Port 0	Port 1
TCP Port	2000	2001
Baud Rate	115200	115200
Data Bits	8	8
Stop Bits	1	1
Parity	None	None
Override Timeout	10 seconds	10 seconds

Customization

Modify these constants in main.cpp to change the configuration:

#define BAUDRATE_TO_USE (115200)    // Baud rate for both serial ports
#define STOP_BITS (1)               // Number of stop bits
#define DATA_BITS (8)               // Number of data bits  
#define TCP_PORT0_TO_USE (2000)     // TCP port for serial port 0
#define TCP_PORT1_TO_USE (2001)     // TCP port for serial port 1
#define OVERRIDE_TIMEOUT (TICKS_PER_SECOND * 10)  // Override timeout

How It Works

Connection Process

1. Startup: Application initializes both serial ports and begins listening on configured TCP ports
2. Client Connection: When a TCP client connects, a dedicated bridge is established
3. Data Transfer: All data received from the network is sent to the serial port, and vice versa
4. Connection Management: Only one client per serial port at a time

Override Feature

The override timeout prevents stale connections from blocking new clients:

• When a client connects, the listen socket is closed to prevent additional connections
• After the timeout period expires, a new listen socket opens
• If a new client attempts to connect, the old connection is automatically closed
• This handles cases where clients crash or disconnect improperly

Usage

Network Client Connection

Connect to the NetBurner device using any TCP client:

# Connect to serial port 0
telnet <netburner_ip> 2000
 
# Connect to serial port 1  
telnet <netburner_ip> 2001

Example Use Cases

• Remote Serial Console: Access device debug output over network
• Serial Device Control: Control industrial equipment remotely
• Data Logging: Collect serial data from remote sensors
• Protocol Bridging: Convert between network and serial protocols

Architecture

Task Structure

• UserMain Task: Handles serial port 0 and TCP port 2000
• SerialTask2: Handles serial port 1 and TCP port 2001 (lower priority)

Data Flow

TCP Client <-> Network Stack <-> SerialToEthernetFunction <-> Serial Port <-> Connected Device

Technical Details

Buffer Management

• Uses 80-byte buffers for data transfer
• Non-blocking I/O with select() for efficient multiplexing
• Immediate data forwarding (no buffering delays)

Error Handling

• Automatic socket cleanup on network errors
• Graceful handling of serial port errors
• Connection state monitoring and recovery

Performance Considerations

• SerialTask2 runs at lower priority than UserMain
• 2-second select timeout for responsive operation
• Efficient file descriptor monitoring

Building and Deployment

1. Requirements: NetBurner development environment and hardware
2. Compilation: Use standard NetBurner build tools
3. Deployment: Flash to NetBurner device
4. Network Setup: Ensure device has network connectivity

Troubleshooting

Common Issues

No Connection**: Verify network connectivity and TCP port accessibility Data Loss**: Check baud rate and serial settings match connected device Stale Connections**: Override timeout will eventually clear blocked connections Performance Issues**: Consider adjusting buffer sizes for high-throughput applications

Debug Output

The application provides console output showing:

• Listen socket creation
• Client connections and disconnections
  
• Override timeout events
• Socket file descriptor information