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JSON-RPC 2.0 for Elixir.

Use the included TCP/TLS server/client, JSON-in-the-body HTTP(S) server/client, or bring your own transport.

See the examples directory as well as the JSONRPC2 docs for examples.

To install, add jsonrpc2 and jason to your list of dependencies in mix.exs:

def deps do
  [{:jsonrpc2, "~> 2.0"}, {:jason, "~> 1.0"}]

v2.0 Upgrade


The TCP/TLS server/client default packet format has changed in v2.0, causing backwards incompatibility.

If your existing servers/clients are working fine in line_packet mode, there is no need to change to the new packet format.

However, if you wish to upgrade existing servers/clients to v2.0 safely, you must now pass the line_packet: true option.

Here are some examples of adding the option for both server and client:

# Server option should be added to `opts`
JSONRPC2.Servers.TCP.start_listener(handler, port, name: name, line_packet: true)
JSONRPC2.Servers.TCP.child_spec(handler, port, name: name, line_packet: true)

# Client option should be added to `client_opts`
JSONRPC2.Clients.TCP.start(host, port, name, line_packet: true)


The line-terminated packet format caused the size of the packet to be limited by the size of the socket's receive buffer, causing difficult to diagnose errors when the packet size passed the limit.

The only downside of the new approach is a 4-byte overhead due to a new header indicating the size of the rest of the packet.

In light of the fact that the smallest possible JSON-RPC 2.0 request is approximately 50 bytes, I have decided to make this format the new default in an attempt to follow the principle of least surprise.

What if I want to switch to the new packet format, and uptime is a concern?

Here's an example approach:

  1. Update to v2.0, add line_packet: true, and deploy.
  2. Add a new server listener for each existing one, on a different port, without line_packet: true, and deploy.
  3. Update clients to use the new port, remove line_packet: true, and deploy.
  4. Remove the original server listener for each one you created, and deploy.


Uses jason by default, but you can use any serializer (it doesn't even have to be JSON, technically).

A serializer for jiffy is included as JSONRPC2.Serializers.Jiffy, and legacy users can select Poison if they have included it as a dependency.

To use a different serializer you must configure it in your Mix config. For the jiffy serializer:

config :jsonrpc2, :serializer, JSONRPC2.Serializers.Jiffy

If you are going to use the jiffy serializer, you must add it to your deps instead of jason:

def deps do
  [..., {:jiffy, "~> 1.0"}]

If you use your own serializer, you do not (necessarily) need to add jason or jiffy to your deps.

TCP/TLS server

If you plan to use the TCP/TLS server, you also need to add ranch to your deps.

def deps do
  [..., {:ranch, "~> 1.7"}]

TCP/TLS client

If you plan to use the TCP/TLS client, you also need to add shackle to your deps/apps.

def deps do
  [..., {:shackle, "~> 0.5"}]

HTTP(S) server

If you plan to use the HTTP(S) server, you also need to add plug, cowboy, and plug_cowboy to your deps.

def deps do
  [..., {:plug, "~> 1.8"}, {:cowboy, "~> 2.6"}, {:plug_cowboy, "~> 2.0"}]

HTTP(S) client

If you plan to use the HTTP(S) client, you also need to add hackney to your deps.

def deps do
  [..., {:hackney, "~> 1.15"}]