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Zeromq package

4,874 bytes added, 21:22, 4 March 2016
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>> 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 signififed success.
 
== The functions ==
 
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_errno
Get system errno value.
 
zmq_getsockopt
Get current value of a zeromq socket option.
 
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_strerror
Get the last zmq error string.
 
zmq_unbind
Unbind a previously bound zeromq socket.
 
zmq_version
Get the zeromq library version numbers.
 
= Examples =
 
== 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 ==
 
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>}}
[[Category:Octave-Forge]]
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