# RabbitMQ C AMQP client library

## Introduction

This is a C-language AMQP client library for use with AMQP servers
speaking protocol versions 0-8 and 0-9-1.

 - <http://www.rabbitmq.com/>
 - <http://www.amqp.org/>
 - <http://hg.rabbitmq.com/rabbitmq-c>

*NB*: This library's source code supports *either* 0-8 *or* 0-9-1, not
both simultaneously. Please check carefully that you have the variant
you require.

Announcements regarding the library are periodically made on the
RabbitMQ mailing list and on LShift's blog.

 - <http://lists.rabbitmq.com/cgi-bin/mailman/listinfo/rabbitmq-discuss>
 - <http://www.lshift.net/blog/>
 - <http://www.lshift.net/blog/category/lshift-sw/rabbitmq/>

## Retrieving the code

In addition to the source code for this library, you will require a
copy of `rabbitmq-codegen`. Here is a short `sh` script for retrieving
the necessary pieces:

    hg clone http://hg.rabbitmq.com/rabbitmq-codegen/
    hg clone http://hg.rabbitmq.com/rabbitmq-c/

You will also need a recent python with the simplejson module
installed, and the GNU autotools (autoconf, automake, libtool etc).

## Building the code

Once you have all the prerequisites, change to the `rabbitmq-c`
directory and run

    autoreconf -i

to run the GNU autotools and generate the configure script, followed
by

    ./configure
    make

to build the `librabbitmq` library and the example programs.

## Running the examples

Arrange for a RabbitMQ or other AMQP server to be running on
`localhost` at TCP port number 5672.

In one terminal, run

    ./examples/amqp_listen localhost 5672 amq.direct test

In another terminal,

    ./examples/amqp_sendstring localhost 5672 amq.direct test "hello world"

You should see output similar to the following in the listener's
terminal window:

    Result 1
    Frame type 1, channel 1
    Method AMQP_BASIC_DELIVER_METHOD
    Delivery 1, exchange amq.direct routingkey test
    Content-type: text/plain
    ----
    00000000: 68 65 6C 6C 6F 20 77 6F : 72 6C 64                 hello world
    0000000B:

## Writing applications using `librabbitmq`

Please see the `examples` directory for short examples of the use of
the `librabbitmq` library.

### Threading

You cannot share a socket, an `amqp_connection_state_t`, or a channel
between threads using `librabbitmq`. The `librabbitmq` library is
built with event-driven, single-threaded applications in mind, and
does not yet cater to any of the requirements of `pthread`ed
applications.

Your applications instead should open an AMQP connection (and an
associated socket, of course) per thread. If your program needs to
access an AMQP connection or any of its channels from more than one
thread, it is entirely responsible for designing and implementing an
appropriate locking scheme. It will generally be much simpler to have
a connection exclusive to each thread that needs AMQP service.

### Switching the codebase to the 0-9-1 protocol version

In current releases, the default (trunk) branch of the mercurial
repository hosting the `rabbitmq-c` code is set up for AMQP 0-8
support, with AMQP 0-9-1 support living on a separate mercurial
branch.

NOTE: Protocol versions 0-8 and 0-9-1 are incompatible on the
wire. You cannot use a client library that speaks one protocol version
to communication with a server that speaks the other.

To switch your checked-out copy of the source code to 0-9-1
support,

    (cd rabbitmq-codegen; hg up amqp_0_9_1)
    (cd rabbitmq-c; hg up amqp_0_9_1)

before building the code. If you switch branches after having compiled
the code, make sure to rerun `autoreconf`, `configure`, `make clean`
and `make` after switching branches.