add usage example

examples/client-cert-chain.py

@@ -0,0 +1,70 @@
+import asyncio
+from enum import Enum
+from pathlib import Path
+
+from asyncua import Client, ua
+from asyncua.crypto import security_policies
+from asyncua.crypto.uacrypto import CertProperties
+
+url = "opc.tcp://localhost:4840/freeopcua/server/"
+namespace = "http://examples.freeopcua.github.io"
+
+CERT_BASE = Path(__file__).parent / "examples" / "certificates" / "chain"
+
+
+class CertChain(Enum):
+    INTER1 = CERT_BASE / "inter1.cert.pem"
+    INTER2 = CERT_BASE / "inter2.cert.pem"
+    CLIENT = CERT_BASE / "client.cert.pem"
+
+
+CLIENT_PRIVATE_KEY = CERT_BASE / "client.key.pem"
+
+
+async def main():
+    print(f"Connecting to {url} ...")
+    client = Client(url=url)
+    client.application_uri = "urn:example.org:FreeOpcUa:python-opcua-client"
+
+    # Set communication certificates including chain
+    await client.set_security(
+        security_policies.SecurityPolicyBasic256Sha256,
+        certificate=CertChain.CLIENT.value,
+        private_key=CLIENT_PRIVATE_KEY,
+        private_key_password=None,
+        server_certificate=None,
+        mode=ua.MessageSecurityMode.SignAndEncrypt,
+        certificate_chain=[CertChain.INTER2.value, CertChain.INTER1.value],
+    )
+
+    # Set user authentication certificates including chain
+    await client.load_client_certificate(CertChain.CLIENT.value)
+    await client.load_private_key(CLIENT_PRIVATE_KEY)
+    await client.load_client_chain(
+        [
+            CertProperties(CertChain.INTER2.value),
+            CertProperties(CertChain.INTER1.value),
+        ]
+    )
+
+    async with client:
+        # Find the namespace index
+        nsidx = await client.get_namespace_index(namespace)
+        print(f"Namespace Index for '{namespace}': {nsidx}")
+
+        # Get the variable node for read / write
+        var = await client.nodes.root.get_child(f"0:Objects/{nsidx}:MyObject/{nsidx}:MyVariable")
+        value = await var.read_value()
+        print(f"Value of MyVariable ({var}): {value}")
+
+        new_value = value - 50
+        print(f"Setting value of MyVariable to {new_value} ...")
+        await var.write_value(new_value)
+
+        # Calling a method
+        res = await client.nodes.objects.call_method(f"{nsidx}:ServerMethod", 5)
+        print(f"Calling ServerMethod returned {res}")
+
+
+if __name__ == "__main__":
+    asyncio.run(main())