How can I pass a TCPIP handle to a parfeval worker

In my special case, I need to construct a TCPIP handle before running the parfeval. So I was thinking to pass the TCPIP handle to parfeval. However, it looks like the worker runs under a different workspace than the workspace where TCPIP handle I was constructed. Any idea how to solve this problem ? Thanks

main code

 port = tcpip('192.xxx.xx.xx', xxx); 
 fopen(port);
 Request_message = ['aaaaaa'];
 fwrite(port, Request_message );
 value = []; 
 parpool(2)
 for i = 1:20
   f1 = parfeval(@f1_worker,1,port);
   if ~isempty(value)
     f2 = parfeval(@f2_worker,1,value);
   end
  [completedIdx,value] = fetchNext([f1]);
 end
 fclose(port);
 delete(port);
 delete(gcp('nocreate'));

worker

 function  [message] = f1_worker(port)    
  message =  fread(port);
 end

Answer 1

[Edric Ellis]

The workers executing the body of your parfeval requests are separate processes, so you cannot send objects of class tcpip to the workers. You should instead use parallel.pool.Constant to build the tcpip objects directly on the workers, and use them from there. A bit like this (completely untested):

% We must open the pool up front
parpool(2);
% Build the tcpip on each worker
c = parallel.pool.Constant(@iBuildTcpip);
% Here's the builder function
function port = iBuildTcpip()
  port = tcpip('192.xxx.xx.xx', xxx); 
  fopen(port);
  Request_message = ['aaaaaa'];
  fwrite(port, Request_message );
end

% Now submit parfeval requests using "c"
parfeval(@iDoStuff, 1, c);
% where iDoStuff is something like
function out = iDoStuff(c)
  port = c.Value; % Unpack the parallel.pool.Constant
  out = fread(port);
end

[Minglei Huang]

Thanks for answer, I tried this way before. However, the value c returned is empty.

[Timo Schmid]

I've got the same problem - did you find a solution?