FluentModbus is a .NET library that implements the Modbus protocol (TCP and RTU) for client and server communication. The library provides a full set of function codes (class 0, 1, and partial class 2) including read/write holding registers, coils, discrete inputs, input registers, and combined read-write operations. Both synchronous and asynchronous APIs are available. The server supports multiple unit identifiers, frame validation via a user-defined callback, events for register/coil changes, and configurable endianness. The client exposes high-level generic methods as well as low-level byte-oriented access. The codebase is well-structured with abstract base classes (MobusClient, ModbusServer), separate request handlers for TCP and RTU, and clean separation of concerns. Dependencies are minimal (logging abstractions, I/O, memory). The library includes comprehensive unit tests and samples.