The APRS Internet Network
is a java program that allows the display of
position reports from within a browser. Since I first released this
program a number of different schemes have been developed to place
the APRS data onto the internet. Each of these sites is an island
of data that is not connected to the others. Memory is the only limitation
that javAPRS faces in terms of the number of different sites it may connect
with. However, the servers will quickly become overloaded with connections,
and a dial up connection can quickly become swamped with full data from a
bunch of different sites.
As more APRS sites come on line, it becomes increasingly important to provide
a higher level of connection to improve the efficiency of the system.
APRServe provides a way to provide the Internet APRS backbone. As presently
envisioned, the APRServe network will connect to the TNC servers, and will consolidate
the various reports, messages, and other data, and provide this data to any
number of client programs. Figure 1 shows how the various parts of the
APRS network will interact. I will cover each of these programs and
links separately below.
The TNC server take data from a TNC and makes it available on the internet.
At this time there are two different servers under development, by
Dale Heatherington WA4DSY
Steve Boyle KD6WXD
Both of these programs perform a limited amount od caching, and Steve's has the
ability to relay TIGER maps. At this time, these servers simply place data onto
the internet. There may, in the future, be a way to send messages though specific
TNC servers. However, a number of issues such as user verification need to be
addressed before this is implemented. There will not be any provision for the
wholesale gating of Internet data back onto the VHF of HF nets. The amount of
data on the internet would completely overwhelm the radio side of the network.
Presently there are three clients anticipated for the APRS Internet Network.
javAPRS, being "born" to networking, is fully functional now. MacAPRS, thanks to
Apple's Communication Toolbox, is able, with a public domain tool, to connect to
the network now. It does not handle the full protocol at this time. WinAPRS is
expected to catch up to MacAPRS once the beleagered Sprouls get a chance. I
expect that most "hard core" APRS users will prefer the Mac/WinAPRS client, as
it is faster and has more features than javAPRS. javAPRS is more useful for
casual users, and most especially for newcomers and non-hams, since it is
automatically downloaded and run by the Web browser.
TNC Server to APRServe
All TNC servers should have a link to at least one computer running APRServe.
It is expected that all data received on the TNC will be forwarded to APRServe.
On initial connect, the TNC server should dump all cached data to APRServe.
APRServe sends an initial ?APRS? command to initiate the data dump, the server
can either wait for this request or always dump the full set of data.
TNC Server to Client Programs
Clients have the option of connecting directly to a TNC server. This is especially
useful when data from a particular area is of interest, such as a local
javAPRS page. The TNC Servers may, at their option, provide some consolidation and/or
caching services for clients. Generally though, all data from the TNC will be sent to
the client. No data will be sent from the client to the TNC server.
APRServe to APRServe
APRServe has the ability to link with other copies of itself. In this way the
network can be redundant. Initially, there will be very limited "self-healing"
capabilities to this linkage. This will be an area of future enhancement to make
the network more robust.