If you want to mimic the behaviour of Simulink blocks using a MATLAB script, it might be helpful to look at the underlying S-function of the concerned block. To do this, right-click the Simulink block (in this case it might be the TCP Send or Recieve block), select the "Block Paramerters" option. This should open a dialog box with the name of the underlying S-function (say "sfcn.m"). Now, you can open the S-function and check how the functionalities have been implemented using
in the MATLAB command line. I hope this helps you!