The overhead of one additional remote service call is justified by additional flexibility. The trader returns a list of servers that specified the keywords in their registration. The communication between client and trader follows a text-based protocol implemented on top of sockets . The user interface presents the availability status, price information, etc. to the user. After selecting a specific flight, the client program only contacts the server that provided the information.
Security is an issue in many of the information exchanges outlined above.
The travel agent wants to be sure that the information sent by a specific airline server is authentic, i.e. that the information was not changed by a third party between the client and the server. This is achieved by a digital signature which is appended at the end of the message. In the first lab assignment , you are required to implement the client component with an interface for a travel agent. In order to enhance the service of our flight reservation system, we now consider what is necessary to add new airlines and flights to our system. The design of our client already allows integration of new servers because clients do not include hard-coded information.