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Re: Zero_mq stacked while receiving msg

From: Ardid, Salva
Subject: Re: Zero_mq stacked while receiving msg
Date: Thu, 25 Apr 2019 20:20:18 +0000

El dijous, 25 d’abril de 2019, a les 15:45:05 EDT, JohnD va escriure:

  From: Ardid, Salva [mailto:address@hidden 
  Sent: Thursday, April 25, 2019 12:37 PM
  To: John Donoghue
  Cc: address@hidden
  Subject: Zero_mq stacked while receiving msg
  Unfortunately the receive function below gets stacked in Octave (i.e., when 
obj.isMatlab == 0 ) at the zmq_recv call and I don’t have a clue what might be 
wrong or how to fix it. Please note that other calls to the function seem to 
work fine, and then for whatever reason one of them gets trapped. I tried 
changing the number of bits to very large numbers with no difference. Any help 
is more than appreciated.
  function str = receive(obj)
              if obj.isMatlab
                  msg = libstruct('zmq_msg_t', struct('hidden', zeros(1, 64, 
                  calllib('libzmq', 'zmq_msg_init', msg); % always returns 0
                  msglen = calllib('libzmq', 'zmq_msg_recv', msg, obj.socket, 
                  assert(msglen >= 0, obj.errortext('zmq_msg_recv'));
                  msgptr = calllib('libzmq', 'zmq_msg_data', msg);
                  if not(msgptr.isNull)
                      setdatatype(msgptr, 'uint8Ptr', 1, msglen);
                      str = uint8(msgptr.Value);
                      str = uint8([]);
                  err = calllib('libzmq', 'zmq_msg_close', msg);
                  assert(err == 0, obj.errortext('zmq_msg_close'));
                  % this is all transparent in Octave (internally managed by 
                  str = zmq_recv (obj.socket, 64, 0);
  Stacked ? Not sure what that means.
  Note that in your malab code,  the 'zmq_msg_t' structure that is 64 bytes in 
  That’s not the same as saying the received data will be 64 bytes in length
  So just out of interest sake, try a larger zmq_recv size ... 1024 ?
  Which version of libzmq are you using ?
Hi John,

Thanks for your email.

"Stacked" means that nothing seems to happen, if I run the code with some 
verbose info I get:

> python3 
zeromq loaded
socket done
connection done
receiving msg
msg received
sending msg
msg sent
receiving msg
msg received
sending msg
msg sent
receiving msg
msg received
sending msg
msg sent
receiving msg

And then it stays in last `receiving message` for ever without actually 
receiving it (it would be indicated by `msg received`)

I know, 64 does not need to be the maximum number, however changing that number 
didn't change the behavior. I set it up to 2^31-1, because that is what the 
maximum seems to be in the python side according to an exception (response = 
msgpack.unpackb(self.socket.recv(), raw=False, max_bin_len=2**31-1)

I use libzmq 4.2.5

I don't see what might be wrong. Any help is more than welcome.


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