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ZeroMQ Basics ​

Programming with ZeroMQ ​

  1. Learn ZeroMQ step-by-step. Take is slow and learn to master each of the simple building blocks.
  2. Write nice code. Use variable names that have real words and use consistent indentation.
  3. Test what you make as you make it. Break your code into small chuncks.

The context is one of the most important aspects of ZeroMQ. The context is what you use to create sockets. There should only be one context per process, sometimes more is okay, but be really sure that's what you want before making that your design.

Call zmq_ctx_new() once at the start of a process, and zmq_ctx_destroy()once at the end.

  1. Always clean up when you finish a job. The ZeroMQ objects you need to worry about are messages, sockets, and contexts.
  • Use zmq_send() and zmq_recv() whenever possible as is avoids the need to use zmq_msg_t objects.
  • If you do use zmq_msg_recv(), always release the received message as soon as you’re done with it, by calling zmq_msg_close().
  • Don't open and close lots of sockets. If you are you probably have a design problem.
  • When you exit the program, close your sockets and then call zmq_ctx_destroy() to destroy the context.

Clean Exit with Multithreaded ZeroMQ ​

  1. Do not try to use the same socket from multiple threads, ever.
  2. Shutdown each socket that has ongoing requests by setting a low LINGER value (1 second), and then close the socket. Your language binding should do this for you automatically if you destroy a context.
  3. Destroy the context.

The Life of a ZeroMQ socket ​

  1. Creating and desttorying sockets (with zmq_socket(), zmq_close())
  2. Configuring sockets by setting options on them and checking them if necessary (with zmq_setsockopt(), zmq_getsockopt())
  3. Plugging sockets into the network topology by creating connections (with zmq_bind(), zmq_connect())
  4. Using the sockets to carry data by writing and receiving messages on them (with zmq_send(), zmq_recv())

Sockets are always void pointers, while messages are structures the programmer defines.

You should think of your servers (the ones that call zmq_bind()) as relatively static parts of your application, while the clients (the ones that call zmq_connect()) are more dynamic and can come and go.

ADDITIONAL RESOURCES