How do I inherit the TCPIP class correctly in Matlab?

Question

I wanted to create a TCPIP object inside a class. I have some problems to figure out how to done this.

First I will show a working code snippet:

>> %Creating the TCPIP object
>> TCPIP = tcpip('localhost',1000)

   TCPIP Object : TCPIP-localhost

   Communication Settings 
    RemotePort:         1000
    RemoteHost:         localhost
    Terminator:         'LF'
    NetworkRole:        client

   Communication State 
    Status:             closed
    RecordStatus:       off

   Read/Write State  
    TransferStatus:     idle
    BytesAvailable:     0
    ValuesReceived:     0
    ValuesSent:         0


>> %Changing Buffersize as example
>> TCPIP.OutputBufferSize = 30000

    TCPIP Object : TCPIP-localhost

    Communication Settings 
     RemotePort:         1000
     RemoteHost:         localhost
     Terminator:         'LF'
     NetworkRole:        client

    Communication State 
     Status:             closed
     RecordStatus:       off

    Read/Write State  
     TransferStatus:     idle
     BytesAvailable:     0
     ValuesReceived:     0
     ValuesSent:         0

As you can see the command line output of the Buffersize change is not shown. I can't visualize this correctly but I try to explain: After creating the TCPIP object Matlab creates the variable TCPIP with the value 1x1 tcpip . If I double click this value I can see all properties of the object, including outputBuffersize .

Now I will show my first try of implemantation in class. I tryied to create the tcpip object inside a methode that saves the variable TCPIP (like explained before) inside my class properties.

classdef tcp_test < handle

    properties
        TCPIP
    end

    methods

         %CONSTRUCTOR
         function Obj = tcp_test(~)      
             ipobject(Obj);
         end

         %DECONSTRUCTER
         function delete(~) 
         end

         %Create TCPIP Object
         function ipobject(Obj)
             Obj.TCPIP = tcpip('localhost',1000);
             Obj.TCPIP.OutputBufferSize = 30000;
         end
    end
end

This class example is working with any error output, but I recognized something that seems not working as I expected. After creating the class object ´myTCP = tcp_test´ I tryed to investigate the the Object ´myTCP.TCPIP´ and realized that it looks like empty. Actually all necessary properties are set and I can change them, they are just not shown.

This leads to the original Question: I thought I have to inherit the tcpip class to use the class methods.

I still have the feeling that I still doing something wrong, because of the missing visualisatiuon.

Answer 1

I think this is just a lack of understanding what is displayed in the command window - it's not all of the properties of the object, sometimes just a subset. If you type get( TCPIP ) in the command window, you will see all properties including the OutputBufferSize . Similarly, t = tcp_test; get( t.TCPIP ) t = tcp_test; get( t.TCPIP ) will show the same properties.

You can see, from typing edit tcpip in the command window, that the tcpip class has the following properties:

properties(Hidden, SetAccess = 'public', GetAccess = 'public')
    icinterface
end    

It inherits from the instrument class which is not editable, and will have other properties we can't see the definitions for.

The important thing here is the Hidden attribute. From the docs :

MATLAB does not display in the command window the names and values of properties having protected or private GetAccess or properties whose Hidden attribute is true.

This is why you can't see the property in the workspace. However, you can freely edit the properties, and view them using the general get( TCPIP ) , or a specific get command:

outBuffer = get( TCPIP, 'OutputBuffer' );

More simply done with dot indexing

outBuffer = TCPIP.OutputBuffer;