Timeout does not work for modbus (TCP/IP transport)

 m = modbus('tcpip', '192.168.15.25', 502, 'Timeout', 1)
 m = modbus('tcpip', '192.168.15.25', 502)

Running the first command, I was expecting to get timeout error after 1 second, but I get timeout error after 20 seconds, same as running the second command.

 m = modbus('serialrtu','COM3','Timeout',1)

Timeout works with 'serialrtu', but does not work with 'tcpip'.

Matlab 2018b

My IP address: 192.168.15.3

Subnet mask: 255.255.255.0

Could anyone help please? Thanks.

[Enrico Segre]

+1, and for me the timeout on creation is fixed to 120sec, which is even more annoying

Answer 1

[Enrico Segre]

I pinpointed the problem in my installation (2021a) down to method createAndConnect() of /usr/local/MATLAB/R2021a/toolbox/instrument/instrument/+instrument/+interface/+modbus/+tcpip/Modbus.m. This method creates an object of class matlabshared.network.internal.TCPClient. As such, that does have a public property ConnectTimeout,which is neither passed as an argument, nor set in this constructor. I found that as a default, it has value Inf.

To reduce the timeout to for instance 2 seconds I can add a

obj.TcpIpObj.ConnectTimeout=2;

in createAndConnect(), after line 142 of Modbus.m in my version. This of course requires write access to the matlab installation, and obviously is an inflexible and unportable solution.

Answer 2

[Enrico Segre]

Coming back to report, in case someone with the same problem stumbles here: there seems to be a workaround, sanctioned recently by the support staff: https://www.mathworks.com/matlabcentral/answers/2178749-how-to-configure-the-timeout-property-using-the-modbus-function-in-matlab-r2024a

The solution is quoted for r2024a, but it seems to work in my r2020b as well.