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What is chumak?

chumak is a library written in Erlang. It implements the ZeroMQ Message Transport Protocol (ZMTP). chumak supports ZMTP version 3.1.


The goal of chumak application is to provide up-to-date native Erlang implementation of ZMTP.


  1. Resource Property (NEW in 3.1!)
  2. Request-Reply pattern
  3. Publish-Subscribe pattern
  4. Pipeline Pattern
  5. Exclusive Pair Pattern
  6. Version Negotiation
  7. NULL Security Mechanism
  8. CURVE Security Mechanism
  9. Error Handling
  10. Framing
  11. Socket-Type Property & Identity Property
  12. Backwards Interoperability with ZMTP 3.0


You can install chumak from by including the following in your rebar.config:

	{chumak, "X.Y.Z"}

where X.Y.Z is one of the release versions.

For more info on rebar3 dependencies see the rebar3 docs.


See examples. Otherwise use just like a regular Erlang/OTP application.

If you would like to use python tests to try language interop, you need to have pyzmq installed.


$ rebar3 compile

By default, this will try to build a version of the application that does not include support for the CURVE security model.

The environment variable CHUMAK_CURVE_LIB can be used to specify a NIF that implements the encryption functions that are required to support the CURVE security model.

The following values for CHUMAK_CURVE_LIB are supported:

  • nacerl - this is the minimal variant using the tweetnacl C library. By default it is fetched and built from

         Compilation of nacerl requires gcc and make. Since these tools
         may not be available on windows systems, a check on the
         availability of these tools will be done. If they are not
         available the dependency will not be fetched and there will be
         no support for the CURVE security model.
  • nacl - this is similar to nacerl, but it depends on libsodium. The repository for this is The the build process for Chumak will not automatically fetch and build it, but if CHUMAK_CURVE_LIB is set to "nacl", it will be assumed that this library is available and it will be used.

  • enacl - this also depends on libsodium, but it also requires an Erlang VM that supports dirty schedulers. The repository is The build process for Chumak will not automatically fetch and build it, but if CHUMAK_CURVE_LIB is set to "enacl", it will be assumed that this library is available and it will be used.


$ rebar3 eunit -c

The -c will allow you to see the test coverage by running the command below.


$ rebar3 cover

Generate Docs

$ rebar3 edoc


Architecture describes the system structure.

Help Wanted

Would you like to help with the project? Pick any of the issues tagged help wanted and contribute!


See Contributing.


  1. Why another Erlang implementation?

    Because the existing Erlang implementations and bindings are out of date.

  2. Can I use chumak for free?

    Yes, as long as you abide by the terms of the MPLv2 license. In short, you can include this code as a part of a larger work, even commercial. It is only when you modify chumak source code itself that you have to make that change available. Please read the license, as this description is not complete by any means.

  3. Do I have to sign over my copyright when contributing?

    No. Everyone owns the piece of code they contribute. Please see Contributing for details.


This project is licensed under Mozilla Public License Version 2.0. See license for complete license terms.


From Wikipedia:

Chumak (Ukrainian: чумак) is a historic occupation on the territory of the modern Ukraine as merchants or traders, primarily known for the trade in salt.

How to publish new version

This info is here for maintainers - since I keep forgetting how to do this.

  1. Adjust the version of the package in src/
  2. Login to rebar3 hex user auth
  3. Put in your username and your password (ignore the warning) - enter it 2 more times! (weird)
  4. Publish: rebar3 hex publish