OPC UA Server Discovery

Discover available OPC UA servers on the network using opcuaserverinfo

When to Use

• Finding available OPC UA servers on the local network
• Getting the discovery URL or endpoint information for a known server
• Querying server security policies and supported authentication types
• Troubleshooting empty discovery results (LDS issues, certificate trust)
• Setting up prerequisites for OPC UA server discovery

When NOT to Use

• Creating OPC UA client connections (use opcua() directly)
• Reading, writing, or subscribing to OPC UA node values
• Configuring OPC UA connection security (message security, certificates)
• Working with non-OPC UA protocols (Modbus, MQTT)
• Discovering OPC Classic servers (OPC DA, OPC HDA)

Workflow

1. Check prerequisites

Before calling opcuaserverinfo, ensure:

1. The OPC UA Local Discovery Service (LDS) is installed and running
2. The target server is registered with the LDS
3. The server's certificate is trusted by the LDS certificate store at

C:\ProgramData\OPC Foundation\UA\pki\trusted\certs\

Warning: A pki\ folder may also exist under UA\Discovery\ — that is a backward-compatibility fallback from older LDS deployments. The primary store is UA\pki\. Always place certificates in UA\pki\trusted\certs\.

See references/lds-setup-and-troubleshooting.md for paths and setup details.

2. Discover servers

Preferred approach — LDS-based discovery (finds all registered servers):

serverInfo = opcuaserverinfo('localhost');

A single call to opcuaserverinfo with a hostname queries that host's LDS on port 4840. The LDS returns information about ALL servers registered with it. Do not scan IP ranges or iterate over hosts — the LDS aggregates this.

Alternative — direct endpoint discovery (when you know the server URL):

serverInfo = opcuaserverinfo('opc.tcp://myserver:53530/OPCUA/SimulationServer');

Use this when connecting to a specific known server that may not be registered with the LDS, or when the LDS is not available.

3. Inspect results

for k = 1:numel(serverInfo)
    fprintf('Server: %s (port %d)\n', serverInfo(k).Hostname, serverInfo(k).Port);
    fprintf('  Best security: %s / %s\n', ...
        serverInfo(k).BestMessageSecurity, serverInfo(k).BestChannelSecurity);
    fprintf('  Endpoints: %d available\n', numel(serverInfo(k).Endpoints));
end

4. Connect to a discovered server

uaClient = opcua(serverInfo(1));
connect(uaClient);

The opcua() function accepts a ServerInfo object directly — no need to extract hostname and port manually.

Key Functions

There is no `opcuaserverinfo(hostname, port)` syntax. To specify a port, use the discovery URL form: opcuaserverinfo('opc.tcp://hostname:port').

opc.ua.ServerInfo Properties

Note: opc.ua.ServerInfo has Description, not Name. The Name property belongs to opc.ua.Client, not ServerInfo.

opc.ua.EndpointDescription Properties

Patterns

Discover all servers via LDS

serverInfo = opcuaserverinfo('localhost');
if isempty(serverInfo)
    disp('No servers found. Check LDS prerequisites.');
else
    disp(serverInfo);
end

Discover a specific server by URL

serverInfo = opcuaserverinfo('opc.tcp://myserver:53530/OPCUA/SimulationServer');
disp(serverInfo);

Filter servers by authentication type

serverInfo = opcuaserverinfo('localhost');
anonServers = findAuthentication(serverInfo, 'Anonymous');
certServers = findAuthentication(serverInfo, 'Certificate');

Pass discovery result to opcua() for connection

serverInfo = opcuaserverinfo('localhost');
uaClient = opcua(serverInfo(1));
connect(uaClient);

Common Mistakes

Conventions

• Always prefer LDS-based discovery (opcuaserverinfo(hostname)) over direct endpoint queries when finding all servers on a network
• Always mention the three LDS prerequisites when discussing discovery setup
• Use serverInfo.Description for display — not Name (which doesn't exist)
• Pass the ServerInfo object directly to opcua() — don't extract hostname/port manually
• When discovery returns empty, do NOT assume the LDS is down — first verify with sc query UALDS, then check server registration, then certificate trust (in that order)

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Copyright 2026 The MathWorks, Inc.

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