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

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Vecta Matlab
Vecta Matlab 2019-3-26
编辑： Enrico Segre 2022-10-26
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.

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回答（1 个）

Enrico Segre
Enrico Segre 2022-10-26
编辑：Enrico Segre 2022-10-26
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.

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