Basic Client#

The opcuaclient utility provides a way to discover server endpoints, browse the address space, and read/write/subscribe to node values on a remote OPC-UA server.

Usage#

opcuaclient.py [OPTIONS] <service> ... <host> [-p <port>]

Where <host> specifies the target server (IP address or hostname, or a full opc.tcp:// endpoint URL), and port (default 4840) is the TCP port. See opcuaclient.py --help for the full set of authentication and secure-channel options (username/password, certificate-based user tokens, --security-policy/--security-mode).

Discovering Endpoints#

opcuaclient.py endpoints <host>

The endpoints (aliases e, discover) command performs an unauthenticated GetEndpoints call and lists every endpoint the server advertises, together with its security policy, security mode and supported user token types.

Browsing the Address Space#

opcuaclient.py browse <host>
opcuaclient.py browse "ns=2;i=1" <host>
opcuaclient.py browse --recursive --values <host>
opcuaclient.py browse -r --maxdepth 3 <host>

The browse (alias b) command lists the children of a node (default: the Objects folder) as a tree, showing each child’s display name, node class (Object, Variable, Method, …) and NodeId.

-r, --recursive#: Descend into every child node instead of listing only a single level, building a full tree of the address space rooted at the given node.

--maxdepth DEPTH#: Limit how many levels deep --recursive descends (default: 10). Has no effect without --recursive.

-V, --values#: Additionally read and display the current value of every Variable node encountered.

Reading and Writing Values#

opcuaclient.py read "ns=2;i=2" <host>
opcuaclient.py write "ns=2;i=3" "'FAULT'" <host>

read/write operate on a single node’s value, addressed by its NodeId. Use endpoints/browse to discover the actual identifiers exposed by a given server rather than assuming a particular numbering scheme – NodeId syntax (numeric ns=2;i=2 vs. string ns=2;s=Name) is server-defined.

Subscribing to Data Changes#

opcuaclient.py subscribe "ns=2;i=2" "ns=2;i=4" --duration 30 <host>

subscribe (alias sub) creates a subscription for one or more nodes and prints each data-change notification as it arrives, for a configurable --duration and/or --count.

Note

subscribe options (--interval/--duration/--count) are consumed by argparse’s subparser and must appear before <host>, not after it.