Enable Server Ports. Those three words have baffled me for years.
It's a menu item, under Interface, on
Xastir and I've been
wondering what it does for a while. I had searched the Internet before
without a positive result but last night I hit
Okay, maybe not gold but I did hit the online version of the Xastir man
page (who reads the man
pages anyway?). On the man page it clearly calls out how to interact
with this switch:
Enable these ports on this menu: "Interface->Enable Server
TCP:2023 Bidirectional TCP port for clients to connect
to. Requires login if client will be transmitting.
UDP:2023 Unidirectional UDP input port for clients to inject
packets. See the documentation for the format.
Hmm, this would make it seem I could share out my RF APRS connection
with other APRS clients on my
LAN. Bingo! A
quick modification to iptables and setting up my APRSdroid software to
connect to my APRS computer yielded APRS stations coming across the
radio showing up directly on my phone! Nice! I was using a TCP
connection so I am able to [STRIKEOUT:transmit and] receive on my
Android device using the TNC and radio upstairs in my shack.
WG3K>APX204,K3CAL-1,WIDE2-1:}WG3K-5>APDR13,TCPIP,WG3K*:=3841.14N/07632.08W$202/005/A==-00052 CALV ARES EC WL2K-1
Where is this useful?
This would be extremely useful anywhere you have multiple APRS clients
but only a single RF connection (and who wants ten different APRS
stations at a single location?). Think EOCs where you have multiple
stations setup. Each station could have their own APRS client where
they could monitor the status of other stations, update resources, and
send and receive messages.
For sharing situational awareness information this is great as well.
Using a UDP
connection, several APRS clients could be connected to Xastir as
"read-only". Think the big situational awareness screens or information
screens for bike races and marathons.
If there were a downside to this implementation it's that it doesn't
appear these stations will show up on the Internet. [STRIKEOUT:That
TCPIP in the packet stream should tell any I-gate that the packet has
already come across the APRS-IS and shouldn't
be passed. This isn't a problem if all your stations you want to
communicate with are on RF but if some are coming across another TCP/IP
network... well, there will likely be problems. I haven't tested if
this affects incoming packets marked as TCPIP but it's on my list.]
Update: 2016-03-27 @ 1812z
After discussing what I was seeing with some Xastir
I realized that what I was seeing was expected. The feature was
designed to have a master computer on the APRS network with other
clients hanging off that master that were getting everything that the
master was seeing but couldn't actually transmit back out to the
network. I was actually making this happen by adding my phone's
callsign into the nws-stations.txt file that forces the client to
transmit those packets, as third-party packets, over the air.
So there you go, Enable Server Ports is a pretty neat feature but one
that will require a bit of work to understand the limitations. Sharing
a single RF connection with a bunch of APRS clients could be very
useful. I'll continue to test out the functionality and see how much of
a load I can put on the server. Updates to this article will be