A framework to build fast and reliable Modbus-powered applications.
Cargo crate: https://crates.io/crates/rmodbus
rmodbus is not a yet another Modbus server. rmodbus is a set of tools to quickly build Modbus-powered applications.
rmodbus is transport and protocol independent
rmodbus is platform independent
can be easily used in blocking, async (non-blocking) applications
tuned for speed and reliability
provides a set of tools to easily work with Modbus context
supports server frame processing for Modbus TCP/UDP and RTU
server context can be easily, managed, imported and exported
Yes, there's no server included. You build the server by your own. You choose protocol, technology and everything else. rmodbus just process frames and works with Modbus context.
Here's an example of a simple TCP blocking server:
```rust use std::io::{Read, Write}; use std::net::TcpListener; use std::thread; use rmodbus::server::{ModbusFrame, ModbusProto, process_frame};
fn tcpserver(unit: u8, listen: &str) {
let listener = TcpListener::bind(listen).unwrap();
println!("listening started, ready to accept");
for stream in listener.incoming() {
thread::spawn(move || {
println!("client connected");
let mut stream = stream.unwrap();
loop {
let mut buf: ModbusFrame = [0; 256];
if stream.read(&mut buf).unwrapor(0) == 0 {
return;
}
let response: Vec
There are also examples for Serial-RTU and UDP in examples folder (if you're reading this text somewhere else, visit rmodbus project repository.
The rule is simple: one standard Modbus context per application. 10k+10k 16-bit registers and 10k+10k coils is usually more than enough. This takes about 43Kbytes of RAM, but if you need to reduce context size, download library source and change CONTEXT_SIZE constant in "context.rs".
rmodbus server context is thread-safe, easy to use and has a lot of functions.
The context is created automatically, as soon as the library is imported. No any additional action is required.
Every time Modbus context is accessed, a context mutex must be locked. This slows down a performance, but guarantees that the context always has valid data after bulk-set or 32-bit data types were written. So make sure your application locks context only when required and only for a short period time.
There are two groups of context functions:
High-level API: simple functions like get_coil automatically lock the context but do this every time when called. Use this for testing or if the speed is not important.
Advanced way is to use low-level API, lock the context manually and then call proper functions, like set, set_f32 etc.
Take a look at simple PLC example:
```rust use rmodbus::server::context;
fn looping() { loop { // READ WORK MODES ETC let mut ctx = context::CONTEXT.lock().unwrap(); let param1 = context::get(1000, &ctx.holdings).unwrap(); let _param2 = context::getf32(1100, &ctx.holdings).unwrap(); // ieee754 f32 let param3 = context::getu32(1200, &ctx.holdings).unwrap(); // u32 let cmd = context::get(1500, &ctx.holdings).unwrap(); context::set(1500, 0, &mut ctx.holdings).unwrap(); match cmd { 1 => { let _ = context::savelocked("/tmp/plc1.dat", &ctx).maperr(|| { eprintln!("unable to save context!"); }); } _ => {} } drop(ctx); // does the same but slower //let _param1 = context::getholding(1000); //let param2 = context::getholdingf32(1100); //let _param3 = context::getholdingu32(1200); // ============================================== // DO SOME JOB // .......... // WRITE RESULTS let mut ctx = context::CONTEXT.lock().unwrap(); context::set(0, true, &mut ctx.coils).unwrap(); context::setbulk(10, &(vec![10, 20]), &mut ctx.holdings).unwrap(); context::set_f32(20, 935.77, &mut ctx.inputs).unwrap(); } } ```
To let the above program communicate with outer world, Modbus server must be up and running in the separate thread, asynchronously or whatever is preferred.
Planned.