RabbitMQ is a complete and highly reliable enterprise messaging system based on the emerging AMQP standard

Rabbits for Dummies
Queuing with RabbitMQ and PHP, part#1
Publishing messages to RabbitMQ with PHP, part#2
Consuming RabbitMQ messages with PHP, part#3
RabbitMQ Management API Client documentation

By default, the guest user is prohibited from connecting to the broker remotely; it can only connect over a loopback interface (i.e. localhost). This applies both to AMQP and to any other protocols enabled via plugins. Any other users you create will not (by default) be restricted in this way.

This is configured via the loopback_users item in the configuration file.

If you wish to allow the guest user to connect from a remote host, you should set the loopback_users configuration item to []. A complete rabbitmq.config which does this would look like:

[{rabbit, [{loopback_users, []}]}].