feat: Implement an exemplary OPC UA subscriber

Cargo.toml

@@ -13,6 +13,7 @@ categories = ["command-line-utilities"]
 
 
 [dependencies]
+opcua = { version = "0.12.0", features = ["client", "console-logging"] }
 
 [dev-dependencies]
 opcua = { version = "0.12.0", features = ["server", "console-logging"] }

src/main.rs

@@ -1,3 +1,6 @@
+mod simple_opc_ua_subscriber;
+
 fn main() {
     println!("Hello, voraus!");
+    simple_opc_ua_subscriber::launch_subscriber().unwrap();
 }

src/simple_opc_ua_subscriber.rs

@@ -0,0 +1,90 @@
+use std::sync::Arc;
+
+use opcua::client::prelude::*;
+use opcua::sync::RwLock;
+
+const DEFAULT_URL: &str = "opc.tcp://127.0.0.1:4855";
+
+pub fn launch_subscriber() -> Result<(), ()> {
+    // Optional - enable OPC UA logging
+    opcua::console_logging::init();
+
+    // Make the client configuration
+    let mut client = ClientBuilder::new()
+        .application_name("Simple Subscriber")
+        .application_uri("urn:SimpleSubscriber")
+        .product_uri("urn:SimpleSubscriber")
+        .trust_server_certs(true)
+        .create_sample_keypair(true)
+        .session_retry_limit(5)
+        .client()
+        .unwrap();
+
+    if let Ok(session) = client.connect_to_endpoint(
+        (
+            DEFAULT_URL.as_ref(),
+            SecurityPolicy::None.to_str(),
+            MessageSecurityMode::None,
+            UserTokenPolicy::anonymous(),
+        ),
+        IdentityToken::Anonymous,
+    ) {
+        if let Err(result) = subscribe_to_variables(session.clone(), 2) {
+            println!(
+                "ERROR: Got an error while subscribing to variables - {}",
+                result
+            );
+        } else {
+            // Loops forever. The publish thread will call the callback with changes on the variables
+            let _ = Session::run(session);
+        }
+    }
+    Ok(())
+}
+
+fn subscribe_to_variables(session: Arc<RwLock<Session>>, ns: u16) -> Result<(), StatusCode> {
+    let session = session.read();
+    // Creates a subscription with a data change callback
+    let subscription_id = session.create_subscription(
+        10.0,
+        10,
+        30,
+        0,
+        0,
+        true,
+        DataChangeCallback::new(|changed_monitored_items| {
+            println!("Data change from server:");
+            changed_monitored_items
+                .iter()
+                .for_each(|item| print_value(item));
+        }),
+    )?;
+    println!("Created a subscription with id = {}", subscription_id);
+
+    // Create some monitored items
+    let items_to_create: Vec<MonitoredItemCreateRequest> = ["ticks_since_launch"]
+        .iter()
+        .map(|v| NodeId::new(ns, *v).into())
+        .collect();
+    let _ = session.create_monitored_items(
+        subscription_id,
+        TimestampsToReturn::Both,
+        &items_to_create,
+    )?;
+
+    Ok(())
+}
+
+fn print_value(item: &MonitoredItem) {
+    let node_id = &item.item_to_monitor().node_id;
+    let data_value = item.last_value();
+    if let Some(ref value) = data_value.value {
+        println!("Item \"{}\", Value = {:?}", node_id, value);
+    } else {
+        println!(
+            "Item \"{}\", Value not found, error: {}",
+            node_id,
+            data_value.status.as_ref().unwrap()
+        );
+    }
+}