Extend example

examples/rtu-client.rs

@@ -3,30 +3,46 @@
 
 //! Asynchronous RTU client example
 
-#[tokio::main(flavor = "current_thread")]
-async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    use tokio_serial::SerialStream;
+use tokio_modbus::{prelude::*, Address, Quantity, Slave};
+use tokio_serial::SerialStream;
+
+const SERIAL_PATH: &str = "/dev/ttyUSB0";
 
-    use tokio_modbus::prelude::*;
+const BAUD_RATE: u32 = 19_200;
 
-    let tty_path = "/dev/ttyUSB0";
-    let slave = Slave(0x17);
+const SERVER: Slave = Slave(0x17);
 
-    let builder = tokio_serial::new(tty_path, 19200);
-    let port = SerialStream::open(&builder).unwrap();
+const SENSOR_ADDRESS: Address = 0x082B;
 
-    let mut conn = rtu::ClientConnection::new(port);
-    println!("Reading a sensor value");
-    let request = Request::ReadHoldingRegisters(0x082B, 2);
-    let request_context = conn.send_request(request, slave).await?;
-    let Response::ReadHoldingRegisters(value) = conn.recv_response(request_context).await?? else {
+const SENSOR_QUANTITY: Quantity = 2;
+
+#[tokio::main(flavor = "current_thread")]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let builder = tokio_serial::new(SERIAL_PATH, BAUD_RATE);
+    let transport = SerialStream::open(&builder).unwrap();
+
+    let mut connection = rtu::ClientConnection::new(transport);
+
+    println!("Reading sensor values (request/response");
+    let request = Request::ReadHoldingRegisters(SENSOR_ADDRESS, SENSOR_QUANTITY);
+    let request_context = connection.send_request(request, SERVER).await?;
+    let Response::ReadHoldingRegisters(values) =
+        connection.recv_response(request_context).await??
+    else {
         // The response variant will always match its corresponding request variant if successful.
         unreachable!();
     };
-    println!("Sensor value is: {value:?}");
+    println!("Sensor responded with: {values:?}");
+
+    println!("Reading sensor values (call");
+    let mut context = rtu::client_context(connection, SERVER);
+    let values = context
+        .read_holding_registers(SENSOR_ADDRESS, SENSOR_QUANTITY)
+        .await??;
+    println!("Sensor responded with: {values:?}");
 
     println!("Disconnecting");
-    conn.disconnect().await?;
+    context.disconnect().await?;
 
     Ok(())
 }

src/client/rtu.rs

@@ -5,6 +5,8 @@
 
 use tokio::io::{AsyncRead, AsyncWrite};
 
+use crate::prelude::rtu::ClientConnection;
+
 use super::*;
 
 /// Connect to no particular Modbus slave device for sending
@@ -21,7 +23,16 @@ pub fn attach_slave<T>(transport: T, slave: Slave) -> Context
 where
     T: AsyncRead + AsyncWrite + Debug + Unpin + Send + 'static,
 {
-    let client = crate::service::rtu::Client::new(transport, slave);
+    let connection = ClientConnection::new(transport);
+    client_context(connection, slave)
+}
+
+/// Creates a client/server connection.
+pub fn client_context<T>(connection: ClientConnection<T>, server: Slave) -> Context
+where
+    T: AsyncRead + AsyncWrite + Debug + Unpin + Send + 'static,
+{
+    let client = crate::service::rtu::Client::new(connection, server);
     Context {
         client: Box::new(client),
     }

src/service/rtu.rs

@@ -96,8 +96,7 @@ impl<T> Client<T>
 where
     T: AsyncRead + AsyncWrite + Unpin,
 {
-    pub(crate) fn new(transport: T, slave: Slave) -> Self {
-        let connection = ClientConnection::new(transport);
+    pub(crate) fn new(connection: ClientConnection<T>, slave: Slave) -> Self {
         let slave_id = slave.into();
         Self {
             connection: Some(connection),
@@ -149,7 +148,6 @@ where
 
 #[cfg(test)]
 mod tests {
-
     use core::{
         pin::Pin,
         task::{Context, Poll},
@@ -158,6 +156,8 @@ mod tests {
 
     use crate::Error;
 
+    use super::*;
+
     #[derive(Debug)]
     struct MockTransport;
 
@@ -190,8 +190,9 @@ mod tests {
     #[tokio::test]
     async fn handle_broken_pipe() {
         let transport = MockTransport;
+        let connection = ClientConnection::new(transport);
         let mut client =
-            crate::service::rtu::Client::new(transport, crate::service::rtu::Slave::broadcast());
+            crate::service::rtu::Client::new(connection, crate::service::rtu::Slave::broadcast());
         let res = client
             .call(crate::service::rtu::Request::ReadCoils(0x00, 5))
             .await;