JBoss.orgCommunity Documentation

Chapter 16. Configuring the Transport

16.1. Understanding Acceptors
16.2. Understanding Connectors
16.3. Configuring the transport directly from the client side.
16.4. Configuring the Netty transport
16.4.1. Configuring Netty TCP
16.4.2. Configuring Netty SSL
16.4.3. Configuring Netty HTTP
16.4.4. Configuring Netty Servlet

HornetQ has a fully pluggable and highly flexible transport layer and defines its own Service Provider Interface (SPI) to make plugging in a new transport provider relatively straightforward.

In this chapter we'll describe the concepts required for understanding HornetQ transports and where and how they're configured.

One of the most important concepts in HornetQ transports is the acceptor. Let's dive straight in and take a look at an acceptor defined in xml in the configuration file hornetq-configuration.xml.

    <acceptor name="netty">
        <param key="port" value="5446"/>

Acceptors are always defined inside an acceptors element. There can be one or more acceptors defined in the acceptors element. There's no upper limit to the number of acceptors per server.

Each acceptor defines a way in which connections can be made to the HornetQ server.

In the above example we're defining an acceptor that uses Netty to listen for connections at port 5446.

The acceptor element contains a sub-element factory-class, this element defines the factory used to create acceptor instances. In this case we're using Netty to listen for connections so we use the Netty implementation of an AcceptorFactory to do this. Basically, the factory-class element determines which pluggable transport we're going to use to do the actual listening.

The acceptor element can also be configured with zero or more param sub-elements. Each param element defines a key-value pair. These key-value pairs are used to configure the specific transport, the set of valid key-value pairs depends on the specific transport be used and are passed straight through to the underlying transport.

Examples of key-value pairs for a particular transport would be, say, to configure the IP address to bind to, or the port to listen at.

Whereas acceptors are used on the server to define how we accept connections, connectors are used by a client to define how it connects to a server.

Let's look at a connector defined in our hornetq-configuration.xml file:

    <connector name="netty">
        <param key="port" value="5446"/>

Connectors can be defined inside a connectors element. There can be one or more connectors defined in the connectors element. There's no upper limit to the number of connectors per server.

You make ask yourself, if connectors are used by the client to make connections then why are they defined on the server? There are a couple of reasons for this:

How do we configure a core ClientSessionFactory with the information that it needs to connect with a server?

Connectors are also used indirectly when directly configuring a core ClientSessionFactory to directly talk to a server. Although in this case there's no need to define such a connector in the server side configuration, instead we just create the parameters and tell the ClientSessionFactory which connector factory to use.

Here's an example of creating a ClientSessionFactory which will connect directly to the acceptor we defined earlier in this chapter, it uses the standard Netty TCP transport and will try and connect on port 5446 to localhost (default):

Map<String, Object> connectionParams = new HashMap<String, Object>();

TransportConfiguration transportConfiguration = 
    new TransportConfiguration(

ServerLocator locator = HornetQClient.createServerLocatorWithoutHA(transportConfiguration);

ClientSessionFactory sessionFactory = locator.createClientSessionFactory();

ClientSession session = sessionFactory.createSession(...);


Similarly, if you're using JMS, you can configure the JMS connection factory directly on the client side without having to define a connector on the server side or define a connection factory in hornetq-jms.xml:

Map<String, Object> connectionParams = new HashMap<String, Object>();

connectionParams.put(org.hornetq.core.remoting.impl.netty.TransportConstants.PORT_PROP_NAME, 5446);

TransportConfiguration transportConfiguration = 
    new TransportConfiguration(

ConnectionFactory connectionFactory = HornetQJMSClient.createConnectionFactoryWithoutHA(JMSFactoryType.CF, transportConfiguration);

Connection jmsConnection = connectionFactory.createConnection();


Out of the box, HornetQ currently uses Netty, a high performance low level network library.

Our Netty transport can be configured in several different ways; to use old (blocking) Java IO, or NIO (non-blocking), also to use straightforward TCP sockets, SSL, or to tunnel over HTTP or HTTPS, on top of that we also provide a servlet transport.

We believe this caters for the vast majority of transport requirements.

Netty TCP is a simple unencrypted TCP sockets based transport. Netty TCP can be configured to use old blocking Java IO or non blocking Java NIO. We recommend you use the Java NIO on the server side for better scalability with many concurrent connections. However using Java old IO can sometimes give you better latency than NIO when you're not so worried about supporting many thousands of concurrent connections.

If you're running connections across an untrusted network please bear in mind this transport is unencrypted. You may want to look at the SSL or HTTPS configurations.

With the Netty TCP transport all connections are initiated from the client side. I.e. the server does not initiate any connections to the client. This works well with firewall policies that typically only allow connections to be initiated in one direction.

All the valid Netty transport keys are defined in the class org.hornetq.core.remoting.impl.netty.TransportConstants. Most parameters can be used either with acceptors or connectors, some only work with acceptors. The following parameters can be used to configure Netty for simple TCP:

We also provide a Netty servlet transport for use with HornetQ. The servlet transport allows HornetQ traffic to be tunneled over HTTP to a servlet running in a servlet engine which then redirects it to an in-VM HornetQ server.

The servlet transport differs from the Netty HTTP transport in that, with the HTTP transport HornetQ effectively acts a web server listening for HTTP traffic on, e.g. port 80 or 8080, whereas with the servlet transport HornetQ traffic is proxied through a servlet engine which may already be serving web site or other applications. This allows HornetQ to be used where corporate policies may only allow a single web server listening on an HTTP port, and this needs to serve all applications including messaging.

Please see the examples for a full working example of the servlet transport being used.

To configure a servlet engine to work the Netty Servlet transport we need to do the following things:

Heres a list of the init params and what they are used for

The servlet pattern configured in the web.xml is the path of the URL that is used. The connector param servlet-path on the connector config must match this using the application context of the web app if there is one.

Its also possible to use the servlet transport over SSL. simply add the following configuration to the connector:

    <connector name="netty-servlet">
         <param key="host" value="localhost"/>
         <param key="port" value="8443"/>
         <param key="use-servlet" value="true"/>
         <param key="servlet-path" value="/messaging/HornetQServlet"/>
         <param key="ssl-enabled" value="true"/>
         <param key="key-store-path" value="path to a keystoree"/>
         <param key="key-store-password" value="keystore password"/>

You will also have to configure the Application server to use a KeyStore. Edit the server.xml file that can be found under server/default/deploy/jbossweb.sar of the Application Server installation and edit the SSL/TLS connector configuration to look like the following:

<Connector protocol="HTTP/1.1" SSLEnabled="true"
           port="8443" address="${jboss.bind.address}"
           scheme="https" secure="true" clientAuth="false"
           keystoreFile="path to a keystore"
           keystorePass="keystore password" sslProtocol = "TLS" />

In both cases you will need to provide a keystore and password. Take a look at the servlet ssl example shipped with HornetQ for more detail.