# Querying Stations

There are several types of queries one APRS station can make to another. The most common, requesting an updated position report, is automatically issued on a Locate->Station request if YAAC doesn't have recent position information about the requested station. Other common queries include:

- Query->Station Direct: The list of stations heard directly (not via digipeaters or IGates) by the queried station
- Query->Station Heard: How many messages have been heard by the queried station from a third station
- Query->Station Ping and Query->Station Trace: The path from the queried station to the querying station (using either the ?PING? or ?APRST queries)
- Query->Station Status: What is the remote station's status message?
- Query->Station SW Version: a description of the software being executed on the queried station. Note this query is presently supported only by YAAC, and KJ4ERJ's APRSIS/32 and APRSIS/CE, and will probably be ignored by other stations.

In addition, YAAC can make broadcast queries to search for RF-local stations, either any APRS station, or those performing I-gate or weather station functions. These broadcast queries can only be used when YAAC has a RF connection.

Also, YAAC can broadcast QRU requests to find out about local resources of various types. Some of the standard QRU groups that are commonly used are:

group name | meaning
--- | ---
AMBU | ambulance
CLUB | ham radio club
ECHO | Echolink
FIRE | fire station
FOOD | restaurants
FUEL | gas/petrol stations
HOSP | hospitals
LIFEBOAT | lifeboats
LTHS | lighthouses
POLI | police stations
POST | post offices
RD13 | D-Star 13cm repeaters
RD23 | D-Star 23cm repeaters
RD2M | D-Star 2m repeaters
RD3C | D-Star 3cm repeaters
RD70 | D-Star 70cm repeaters
RP10 | analog 10m repeaters
RP13 | analog 13cm repeaters
RP23 | analog 23cm repeaters
RP2M | analog 2m repeaters
RP3C | analog 3cm repeaters
RP6M | analog 6m repeaters
RP70 | analog 70cm repeaters
RT13 | television 13cm repeaters
RT23 | television 23cm repeaters
RT3C | television 3cm repeaters
SRAIL | steam railroad
STOR | Amateur Radio stores
T2SRV | approximate locations of Tier 2 APRS-IS servers
VETE | veterinarians
WOTA | Wainwrights On The Air peaks

To find out what QRU codes are in use in your area, send the default query INFO; every QRU server station in range will report the QRU codes they serve and their maximum range.

YAAC can also send and receive lists of tactical callsigns (aliases) in use by RF-local stations and objects; this message interchange is compatible with Xastir and APRS+SA.

The APRS-standard and custom queries that YAAC will respond to are:

Directed query code | Response
--- | ---
?? | This list of query commands recognized by YAAC.
?ABOUT | The version of YAAC software being used.
?ALOHA | The current radius of the Aloha circle for this YAAC station.
?APRSD | The list of directly heard stations.
?APRSH callsign | The number of messages heard from the specified station for each of the last 8 hours.
?APRSL | The list of stations considered local for I-Gating by this station.
?APRSM | Immediately retransmit all unacknowledged messages transmitted to the requesting station.
?APRSO | Immediately transmit all objects and items controlled by this station.
?APRSP | Immediately transmit the current position of this station.
?APRSS | Immediately transmit the current status message of this station.
?APRST | A message with the path from the requesting station to the queried station.
?APRSV | The version of YAAC software being used.
?IGATE | If this station is functioning as an I-Gate, the I-Gate statistics for this station.
?PING? | A message with the path from the requesting station to the queried station.
?QUERIES | This list of query commands recognized by YAAC.
?UP | Immediately transmit the duration of time this instance of YAAC has been running.
?VER | The version of software being used.
?WX | If this station has a weather station attached, immediately send the station position and a positionless weather message.
?YDBG | Report debugging information about the local YAAC station, including memory consumption, station/object quantity being monitored, current map pan and zoom, and thread status.

Broadcast query code | Response
--- | ---
?APRS? | Immediately transmit the current position of this station.
?IGATE? | If this station is functioning as an I-Gate, the I-Gate statistics for this station.
?WX? | If this station has a weather station attached, immediately send the station position and a positionless weather message.

Broadcast message destination | Meaning
--- | ---
QRU | ask for local resources
TACTICAL | send or receive tactical callsign aliases for real callsign-SSIDs