add web protocols, modbus, and improve system-setup documentation

Author: knro

drivers/communications/README.md

@@ -21,6 +21,8 @@ This comprehensive guide covers all methods for communicating with hardware devi
 | **USB Bulk** | Direct USB control with bulk transfers | libusb | DSLR shutters, custom USB devices | [USB Guide](usb/) |
 | **HID** | USB Human Interface Devices | hidapi | Filter wheels, focusers, keypads | [HID Guide](hid/) |
 | **GPIO** | Raspberry Pi / Linux GPIO pins | libgpiod | Relays, switches, sensors, PWM | [GPIO Guide](gpio/) |
+| **Modbus** | Industrial devices (PLCs, relays, sensors) | nanomodbus (built-in) | Relay boards, automation equipment | [Modbus Guide](modbus/) |
+| **Web Protocols** | REST APIs, HTTP services, JSON data | cpp-httplib, nlohmann/json | Cloud devices, IoT, web APIs | [Web Protocols Guide](web-protocols/) |
 
 ## Communication Methods Overview
 
@@ -54,6 +56,22 @@ For specialized hardware that doesn't fit the plugin model:
 - Direct access to device features
 - Platform-specific optimizations
 
+### Application Layer Protocols
+
+For modern web-based devices and industrial automation equipment:
+
+- **[Web Protocols](web-protocols/)** - HTTP clients/servers and JSON handling
+- **[Modbus](modbus/)** - Industrial automation protocol (RTU and TCP)
+
+**Advantages:**
+- Industry-standard protocols with wide device support
+- Structured data models and well-defined operations
+- Built-in libraries (nanomodbus included, cpp-httplib available)
+- Suitable for both consumer IoT and industrial applications
+- Extensible to other protocols (WebSocket, MQTT, etc.)
+
+**Important:** The TCP Connection Plugin is designed for raw binary/text communication protocols. For HTTP/REST APIs, use the [Web Protocols Guide](web-protocols/). For Modbus-enabled industrial devices, use the [Modbus Guide](modbus/).
+
 ## Additional Resources
 
 - **[Creating Custom Plugins](custom-plugins/)** - Build your own connection plugin
@@ -78,6 +96,11 @@ For complete working examples, see:
 - **HID**: `indi-sx/sxwheel.cpp` - Starlight Xpress filter wheel
 - **GPIO**: `indi-gpio/indi_gpio.cpp` - Raspberry Pi GPIO driver
 - **I2C**: `indi/libs/indibase/connectionplugins/connectioni2c.cpp` - I2C plugin
+- **Modbus**: `indi/drivers/io/waveshare_modbus_relay.cpp` - Modbus TCP relay control
+- **Web Protocols**: 
+  - HTTP Client: `indi/drivers/auxiliary/ipx800v4.cpp` - REST API consumer
+  - HTTP Server: `indi/drivers/alpaca/indi_alpaca_server.cpp` - REST API provider
+  - JSON Handling: `indi/drivers/auxiliary/alto.cpp` - JSON parsing examples
 
 ## Need Help?