Sending and Receiving Messages
In the last section you learned how to create a new service that simply had the state consisting of a string with the value "Hello World." To accomplish this, the phrase was posted to a DSS port. Messages, which represent a DSS operation on a port, allow other services to read and update the state of a service. In the last example, the phrase "Hello World" represented the state of the service. This phrase was sent to a port, and the result was a SOAP message that appeared in an Internet browser.
A DSS port provides a way for services to communicate by passing messages back and forth. A service can specify one or more ports, and each port contains a data structure that holds the messages sent to the port. By default, ...