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4,874 bytes added ,  21:22, 4 March 2016
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  >> pkg load zeromq
 
  >> pkg load zeromq
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Look at the quick reference for the package:
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  >> help zeromq
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== Differences between C and Octave bindings ==
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The Octave binding is a subset of the C binding of the ZeroMQ library.
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Major differences are:
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1. The octave binding creates a single zeromq context that is used for all zeromq sockets. In the C bindings, the programmer must create a context and use it during socket creation.
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2. only limited zmq_getsockopt and zmq_setsockopt is currently implemented.
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3. functions mostly return true or false for whether they succeeded or failed. In the C binding, 0 signififed success.
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== The functions ==
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zmq_bind
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          Bind a zeromq socket to a endpoint.
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zmq_close
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          Close a zeromq socket.
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zmq_connect
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          Connect a zeromq socket to a endpoint
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zmq_errno
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          Get system errno value.
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zmq_getsockopt
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          Get current value of a zeromq socket option.
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zmq_poll
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          Poll a socket or sockets for a timeout or incoming data
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          available.
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zmq_recv
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          Attempt to read data from a zeromq socket.
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zmq_send
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          Attempt to send data from a zeromq socket.
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zmq_setsockopt
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          Set a zeromq socket option.
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zmq_strerror
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          Get the last zmq error string.
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zmq_unbind
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          Unbind a previously bound zeromq socket.
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zmq_version
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          Get the zeromq library version numbers.
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= Examples =
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== basic request/reply pattern ==
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Example based on client/server example from [http://zguide.zeromq.org/page:all#Ask-and-Ye-Shall-Receive http://zguide.zeromq.org/page:all#Ask-and-Ye-Shall-Receive]
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The client sends a "Hello" to the server which responds back "World". No error checking or data validation is done in the example.
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{{Code|Server code|<syntaxhighlight lang="octave" style="font-size:13px">
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% zeromq package must be installed and loaded to work
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pkg load zeromq
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% dont buffer output
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more off
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printf ("Creating hello world server...\n");
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% create reply socket, and bind it to port 5555
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sock = zmq_socket (ZMQ_REP);
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zmq_bind (sock, "tcp://*:5555");
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printf ("Waiting for clients ...\n");
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% loop forever, waiting for client requests and responding back 
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while (true)
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  recievedata = zmq_recv (sock, 10, 0);
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  printf ("Received Hello\n");
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  zmq_send (sock, "World", 5, 0);
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endwhile
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</syntaxhighlight>}}
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{{Code|Client code|<syntaxhighlight lang="octave" style="font-size:13px">
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% zeromq package must be installed and loaded to work
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pkg load zeromq
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% dont buffer output
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more off
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printf ("Connecting to hello world server...\n");
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% Create socket and connect to server
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sock = zmq_socket (ZMQ_REQ);
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zmq_connect (sock, "tcp://localhost:5555");
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for request_nbr = [1:10]
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  printf ("Sending Hello %d...\n", request_nbr);
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  zmq_send (sock, uint8("Hello"), 5, 0);
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  % try to read up to 10 bytes of reply data.
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  printf ("Waiting for server response %d... (Ctrl-C to exit)\n", request_nbr);
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  recieved = zmq_recv (sock, 10, 0);
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  printf ("Received World %d\n", request_nbr);
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endfor
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zmq_close (sock);
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</syntaxhighlight>}}
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== basic publish subscribe ==
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Example based on client/server example from [http://zguide.zeromq.org/page:all#Getting-the-Message-Out http://zguide.zeromq.org/page:all#Getting-the-Message-Out]
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The server pushes 'weather updates' for random zipcodes. The client subscribes to the server just for zipcode 10001.
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{{Code|Server code|<syntaxhighlight lang="octave" style="font-size:13px">
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% zeromq package must be installed and loaded to work
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pkg load zeromq
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% dont buffer output
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more off
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publisher = zmq_socket (ZMQ_PUB);
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rc = zmq_bind (publisher, "tcp://*:5556");
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assert (rc);
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while (true)
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  %  Get values that will fool the boss
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  zipcode    = 10000 + randi (20);
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  temperature = randi (215) - 80;
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  relhumidity = randi (50) + 10;
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  %  Send message to all subscribers
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  update = sprintf ("%05d %d %d", zipcode, temperature, relhumidity);
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  zmq_send (publisher, update);
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endwhile
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zmq_close (publisher);
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</syntaxhighlight>}}
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{{Code|Client code|<syntaxhighlight lang="octave" style="font-size:13px">
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% zeromq package must be installed and loaded to work
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pkg load zeromq
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% dont buffer output
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more off
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subscriber = zmq_socket (ZMQ_SUB);
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rc = zmq_connect (subscriber, "tcp://localhost:5556");
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assert (rc);
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%  Subscribe to zipcode, default is NYC, 10001
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zipfilter = "10001 ";
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rc = zmq_setsockopt (subscriber, ZMQ_SUBSCRIBE, zipfilter);
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assert (rc);
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%  Process 100 updates
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update_nbr = 0;
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total_temp = 0;
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for update_nbr = 1:100
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  string = char( zmq_recv(subscriber, 128) );
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  [zipcode, temperature, relhumidity, count, errmsg] = sscanf (string, "%d %d %d", "C");
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  fprintf ("recieved a temp for zipcode '%s' of %dF\n", ...
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    zipfilter, temperature);
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  total_temp += temperature;
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endfor
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fprintf ("Average temperature for zipcode '%s' was %dF\n", ...
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  zipfilter, (total_temp / update_nbr));
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zmq_close (subscriber);
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</syntaxhighlight>}}
          
[[Category:Octave-Forge]]
 
[[Category:Octave-Forge]]
28

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