TCP No Block Connect Test

Example Path: examples/TCP/NoBlockConnectTest

TCP No Block Connect Test

Overview

This application demonstrates the difference between blocking and non-blocking TCP connections using NetBurner embedded networking hardware. The program provides an interactive menu system that allows users to test both standard blocking connect() calls and non-blocking NoBlockConnect() calls.

Purpose

The standard TCP connect call will block until the connection is either made or fails. The non-blocking connect call will initiate a TCP connection and return immediately, allowing the application to continue processing while the connection is established in the background.

Features

• Interactive menu-driven interface
• Support for both blocking and non-blocking TCP connections
• Real-time connection state monitoring
• Automatic periodic data transmission (every 5 seconds)
• User input forwarding over established connections
• Display of data received from the remote host
• Configurable destination IP address and port

Menu Options

The application provides the following commands:

• C - Make a connection using standard blocking connect()
• N - Make a connection using non-blocking NoBlockConnect()
• X - Close the current connection
• I - Specify the destination IP address and port number
• ? (or M) - Redisplay this menu
• Any other character - Send the character over the TCP connection (if established)

How It Works

Blocking Connection (C command)

1. Prompts for destination IP and port if not already set
2. Calls connect() which blocks until connection succeeds or fails
3. Immediately reports success or failure
4. Connection is ready for data transmission upon success

Non-Blocking Connection (N command)

1. Prompts for destination IP and port if not already set
2. Calls NoBlockConnect() which returns immediately
3. Reports "Connect started" if the call succeeds
4. Continuously monitors connection state using TcpGetSocketState()
5. Reports "NoBlock connection is done" when TCP_STATE_ESTABLISHED is reached

Automatic Features

• Sends a timestamp message every 5 seconds over established connections
• Displays current TCP state during non-blocking connection attempts
• Forwards any typed characters to the remote host when connected
• Displays any data received from the remote host on the console
• Reports "Connection closed by peer" and cleans up if the remote host disconnects

Technical Details

• Key APIs Used:
  • connect() - Standard blocking TCP connection
  • NoBlockConnect() - Non-blocking TCP connection initiation
  • TcpGetSocketState() - Connection state monitoring
  • Standard socket operations (write(), close())

Build Requirements

• NetBurner development environment
• NetBurner hardware platform
• Standard NetBurner libraries (tcp.h, utils.h, iosys.h, etc.)

Usage Example

1. Run the application on NetBurner hardware
2. When prompted, enter the destination IP address
3. Enter the destination port number
4. Use menu commands to test different connection methods:
   • Try 'C' for blocking connection
   • Try 'N' for non-blocking connection
   • Use 'X' to close connections
   • Use 'I' to change destination settings
5. Type any characters to send data over established connections

Connection State Monitoring

For non-blocking connections, the application continuously displays the TCP state:

• State values correspond to standard TCP states
• Connection is ready when TCP_STATE_ESTABLISHED is reached
• Failed connections will show appropriate error states

Testing with a PC TCP Server

A small Python helper server, tcp_test_server.py, is provided one directory up (in examples/TCP/) to exercise both directions of this example. On each connection it sends a greeting line and prints everything it receives. Anything you type in the server's window is forwarded to the connected device, and the optional --ticks flag also auto-sends a "server tick N" line every 2 seconds.

1. On a PC on the same network, start the server (Python 3):

   python tcp_test_server.py
   

   It listens on port 32001 by default; pass a different port as an argument if desired (e.g. python tcp_test_server.py 5000). Add --ticks to also send a periodic counter (e.g. python tcp_test_server.py --ticks). Make sure your firewall allows inbound connections on that port.

2. On the device, use the I command to enter the PC's IP address and the server's port (32001), then press C (or N) to connect.

3. On the device console you should immediately see the greeting, confirming the receive path:

   HELLO FROM TEST SERVER
   

   Now type some text in the PC server window – it is forwarded over the connection and appears on the device console as you type. If the server was started with --ticks, a "server tick N" line also arrives every 2 seconds.

4. In the PC server window you should see the device's periodic "Time XTick at :NNN" heartbeat, plus any characters you type on the device console (avoid the menu letters C, N, X, I, M and ?, which are intercepted by the menu). This confirms the transmit path.
5. Press X on the device to close the connection. The server reports the connection closed.

Notes

• Only one connection can be active at a time
• IP address and port cannot be changed while connected
• System diagnostics are enabled for debugging (should be disabled in production)
• The application runs in an infinite loop until manually terminated