4. Unicast-Only Operation

One of Ultra Messaging®'s great strengths is its use of the network hardware and protocols to achieve very high performance and scalability. By default, Ultra Messaging uses multicast for topic resolution so that data sources and receivers can find each other.

In general, we recommend the use of multicast whenever possible because it provides the best performance and scalability. However, we recognize that it is not always possible to provide multicast connectivity between the machines. For those cases, we support unicast-only operation.

There are two parts to unicast-only operation. One is to use a unicast form of transport. Ultra Messaging uses TCP by default for transport, but LBT-RU is also available and has some performance advantages. For initial "quick start" testing, we recommend not changing the default TCP.

The second part of unicast-only operation is to use the lbmrd (UM Resolver Daemon) for topic resolution. (NOTE: this does not route message data through a daemon. This is a helper process that lets data sources and receivers find each other.) To enable unicast topic resolution, do the following:

1. Choose one machine to host the resolver daemon and enter the lbmrd command (use lbmrd -h for full instructions).

2. Create a Ultra Messaging configuration file containing:

   context resolver_unicast_daemon [Iface[:Src_Port]->]IP:Dest_Port
   

   where

   • Iface is the interface to use (previously set with resolver_unicast_interface).

   • Src_Port is the source port to use (previously set with resolver_unicast_port).

   • IP is the resolver daemon's IP address (previously set with resolver_unicast_address).

   • Dest_Port is the resolver daemon's UDP port (previously set with resolver_unicast_destination_port).

3. Run the test applications with the option -c filename where filename is the configuration file created in step 2.

See also resolver_unicast_daemon.

Due to the fact that the minimal source programs presented in this document (minsrc.c and minrcv.c) do not allow the use of a configuration file, it is not possible to configure them for unicast-only operation. If multicast operation is not possible on your network, then please use the binary test programs (described in Section 2) which which do allow unicast-only configuration.