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5.3

AServer features

This type of architecture offers a number of advantages:

1

The AServer handles multiple services.

A number of services may be available on one device, handled by a single gateway. For

example, new services may be added without modifying a standard server.

2

The AServer handles multiple clients.

Any process on any processor in the target hardware may open a connection to any service.

The process opening the connection is called the client. Several clients may access the same

service. The gateway will automatically start new services as they are requested.

3

Services are easy to extend.

The AServer enables users to extend the set of services that are available to a user ’sapplica-

tion. The AServer provides the core technology to allow users to create new services by

providing new processes. For example, the iserver service provides terminal text i/o, file

access and system services, which may be expanded by adding new AServer service

processes such as a graphics interface.

4

AServer communications can be fast and efficient.

The communications over the link between gateways use mega-packets, which make effi-

cient use of the available bandwidth. Messages between the client and the service are divided

into packets of up to 1 kbyte. The packets are bundled into mega-packets to send over the

hardware serial link. Packets from different clients and services can be interleaved to reduce

latency.

5

AServer communications are independent of hardware.

When an AServer connection has been established the process can send data messages of

arbitrary length to the service it is connected to, receive data messages of arbitrary length and

disconnect from the service. The gateways are responsible for building and dividing mega-

packets and complying with hardware protocols.