Why do I get a "Check if hostname can be resolved" or "Not enough input arguments" error when connecting to an OPC UA server from MATLAB?

When establishing a connection to an OPC UA server, MATLAB shows the following error in R2022b and earlier:

uaclient = opcua('12.34.56.789')
Error using strncmpi
Not enough input arguments.

Error in opc.ua.Client (line 387)
            if ~strncmpi(this(tI).Hostname, urlParts.Hostname, numel(this(tI).Hostname))

Error in opcua (line 46)
uaObj = opc.ua.Client(varargin{:});

In R2023a and newer:

Could not receive endpoint from URL <...>.
Check if hostname can be resolved.

Answer 1

[MathWorks Support Team]

This issue happens when hostname to IP conversion doesn't occur in the Windows OS. Try the following steps:

1. Navigate to the following path in your Windows Explorer: C:\Windows\System32\drivers\etc\hosts

2. Open the file "hosts".

3. At the bottom of the file "hosts" where there are no "#" symbols, type in the hostname & IP pair for your server. There should be a space between "hostname" and the IP address. It should look something like this:  

12.34.56.789 hostname.domainname.com

This may help MATLAB locate your server.

4. You can then try calling 'opcua' like this:

client = opcua('12.34.56.789', 63500)

Replacing "12.34.56.789" with your server's IP address.