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== package requirements ==
== package requirements ==


The {{Forge|zeromq}} package requires the [http://zeromq.org/ ZeroMQ] libraries and include files to be installed in order to compile.
The {{Forge|zeromq}} package requires the zeromq libraries and include files to be installed in order to compile.


for fedora: yum install zeromq-devel
for fedora: yum install zeromq-devel
for ubuntu: apt install libzmq-dev
for ubuntu: apt install libzmq-dev


== octave installation ==
== octave installation ==


With the [http://zeromq.org/ ZeroMQ] library installed, from octave commmand line:
With the ZeroMQ library installed, from octave commmand line:


  >> pkg install -forge zeromq
  >> pkg install -forge zeromq
= Using it =


Load it before any usage:
Load it before any usage:
Line 23: Line 20:
  >> pkg load zeromq
  >> pkg load zeromq


Look at the quick reference for the package:
  >> help zeromq
== Differences between C and Octave bindings ==
The Octave binding is a subset of the C binding of the ZeroMQ library.
Major differences are:
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.
2. only limited zmq_getsockopt and zmq_setsockopt is currently implemented.
3. functions mostly return true or false for whether they succeeded or failed. In the C binding, 0 signified success.
== The functions ==
iszmq
          Determine whether H is a zeromq socket object.
zmq_bind
          Bind a zeromq socket to a endpoint.
zmq_close
          Close a zeromq socket.
zmq_connect
          Connect a zeromq socket to a endpoint
zmq_curve_keypair
          Generate a random private/public keypair
zmq_curve_public
          Derive the public key from a private key
zmq_disconnect
          Disconnect a zeromq socket from an endpoint.
zmq_errno
          Get system errno value.
zmq_getsockopt
          Get current value of a zeromq socket option.
zmq_has
          Check if the zmq library supports a given feature.
zmq_poll
          Poll a socket or sockets for a timeout or incoming data
          available.
zmq_recv
          Attempt to read data from a zeromq socket.
zmq_send
          Attempt to send data from a zeromq socket.
zmq_setsockopt
          Set a zeromq socket option.
zmq_socket
          Create a zeromq socket.
zmq_strerror
          Get the last zmq error string.
zmq_unbind
          Unbind a previously bound zeromq socket.
zmq_version
          Get the zeromq library version numbers.
zmq_z85_decode
          Decode a z85 encoded string to a binary key.
zmq_z85_encode
          Encode a binary key as Z85 printable text.
= Examples =
The zeromq package comes with a number of examples included in it. They can be opened in octave using:
  >> edit examples/zmq_example1.m
== basic request/reply pattern ==
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]
The client sends a "Hello" to the server which responds back "World". No error checking or data validation is done in the example.
{{Code|Server code|<syntaxhighlight lang="octave" style="font-size:13px">
% zeromq package must be installed and loaded to work
pkg load zeromq
% dont buffer output
more off
printf ("Creating hello world server...\n");
% create reply socket, and bind it to port 5555
sock = zmq_socket (ZMQ_REP);
zmq_bind (sock, "tcp://*:5555");
 
printf ("Waiting for clients ...\n");
 
% loop forever, waiting for client requests and responding back 
while (true)
  recievedata = zmq_recv (sock, 10, 0);
  printf ("Received Hello\n");
  zmq_send (sock, "World", 5, 0);
endwhile
</syntaxhighlight>}}
{{Code|Client code|<syntaxhighlight lang="octave" style="font-size:13px">
% zeromq package must be installed and loaded to work
pkg load zeromq
% dont buffer output
more off
printf ("Connecting to hello world server...\n");
% Create socket and connect to server
sock = zmq_socket (ZMQ_REQ);
zmq_connect (sock, "tcp://localhost:5555");
for request_nbr = [1:10]
  printf ("Sending Hello %d...\n", request_nbr);
  zmq_send (sock, uint8("Hello"), 5, 0);
 
  % try to read up to 10 bytes of reply data.
  printf ("Waiting for server response %d... (Ctrl-C to exit)\n", request_nbr);
  recieved = zmq_recv (sock, 10, 0);
  printf ("Received World %d\n", request_nbr);
endfor
   
zmq_close (sock);
</syntaxhighlight>}}
== basic publish/subscribe pattern ==
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]
The server pushes 'weather updates' for random zipcodes. The client subscribes to the server just for zipcode 10001.
{{Code|Server code|<syntaxhighlight lang="octave" style="font-size:13px">
% zeromq package must be installed and loaded to work
pkg load zeromq
% dont buffer output
more off
publisher = zmq_socket (ZMQ_PUB);
rc = zmq_bind (publisher, "tcp://*:5556");
assert (rc);
while (true)
  %  Get values that will fool the boss
  zipcode    = 10000 + randi (20);
  temperature = randi (215) - 80;
  relhumidity = randi (50) + 10;
  %  Send message to all subscribers
  update = sprintf ("%05d %d %d", zipcode, temperature, relhumidity);
 
  zmq_send (publisher, update);
endwhile
zmq_close (publisher);
</syntaxhighlight>}}
{{Code|Client code|<syntaxhighlight lang="octave" style="font-size:13px">
% zeromq package must be installed and loaded to work
pkg load zeromq
% dont buffer output
more off
subscriber = zmq_socket (ZMQ_SUB);
rc = zmq_connect (subscriber, "tcp://localhost:5556");
assert (rc);
%  Subscribe to zipcode, default is NYC, 10001
zipfilter = "10001 ";
rc = zmq_setsockopt (subscriber, ZMQ_SUBSCRIBE, zipfilter);
assert (rc);
%  Process 100 updates
update_nbr = 0;
total_temp = 0;
for update_nbr = 1:100
  string = char( zmq_recv(subscriber, 128) );
  [zipcode, temperature, relhumidity, count, errmsg] = sscanf (string, "%d %d %d", "C");
 
  fprintf ("recieved a temp for zipcode '%s' of %dF\n", ...
    zipfilter, temperature);
  total_temp += temperature;
endfor
fprintf ("Average temperature for zipcode '%s' was %dF\n", ...
  zipfilter, (total_temp / update_nbr));
zmq_close (subscriber);
</syntaxhighlight>}}




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