Station Capabilities, Queries, and Responses¶
Station CapabilitiesA station may define a set of one or more attributes of the station, known as Station Capabilities. The station transmits its capabilities in response to an IGATE query (see below), using the < Data Type Identifier.
Each capability is a TOKEN or a TOKEN=VALUE pair. More than one capability may be on a line, with each capability separated by a comma.
Currently defined capabilities include:
IGATE,MSG_CNT=n,LOC_CNT=n
where IGATE defines the station as an IGate, MSG_CNT is the number of messages transmitted, and LOC_CNT is the number of “local” stations (those to which the IGate will pass messages in the local RF network).
Queries and Responses¶
There are two types of APRS queries. One is general to all stations and the other is in a message format directed to a single individual station.
Queries always begin with a ?, are one-time transmissions, do not have a message identifier and should not be acknowledged. Similarly the responses to queries are one-time transmissions that also do not have a message identifier, so that they too are not acknowledged.
Each query contains a Query Type (in upper-case). The following Query Types and expected responses are supported:
| Query Type | Query | Response |
|---|---|---|
| APRS | General — All stations query | Station’s position and status |
| APRSD | Directed — Query an individual station for stations heard direct | List of stations heard direct |
| APRSH | Directed — Query if an individual station has heard a particular station | Position of heard station as an APRS Object, plus heard statistics for the last 8 hours |
| APRSM | Directed — Query an individual station for outstanding unacknowledged or undelivered messages | All outstanding messages for the querying station |
| APRSO | Directed — Query an individual station for its Objects | Station’s Objects |
| APRSP | Directed — Query an individual station for its position | Station’s position |
| APRSS | Directed — Query an individual station for its status | Station’s status |
| APRST or PING? | Directed — Query an individual station for a trace (i.e. path by which the packet was heard) | Route trace |
| IGATE | General — Query all Internet Gateways | IGate station capabilities |
| WX | General — Query all weather stations | Weather report (and the station’s position if it is not included in the Weather Report) |
Bytes:
If a queried station has no relevant information to include in a response, it need not respond.
A queried station should ignore any query that it does not recognize.
General QueriesThe format of a general query is as follows:
| General Query Format | ||||||||
|---|---|---|---|---|---|---|---|---|
| ? | Query Type | ? | Target Footprint | |||||
| Lat | , | Long | , | Radius | ||||
| 1 | n | 1 | n | 1 | n | 1 | 4 | |
| Examples Query Typical Response ?APRS? /092345z4903.50N/07201.75W> General query, with standard posit and status reply. >092345zNet Control Center ?APRS?˽34.02,-117.15,0200 /3402.78N11714.02W- General query for stations within a target footprint >Digi on low power of radius 200 miles centered on 34.02 degrees north, 117.15 degrees west, with standard posit and status reply. (Note the leading space in the latitude, as its value is positive, see below). ?IGATE? |
In the case of an ?APRS? query for stations within a particular target footprint, the latitude and longitude parameters are in floating point degrees (not in APRS lat/long position format).
- North and east coordinates are positive values, indicated by a leading ˽
(space).
- South and west coordinates are negative values.
- The radius of the footprint is in miles, expressed as a fixed 4-digit number in whole miles.
All stations inside the specified coverage circle should respond with a Position Report and a Status Report.
Directed Station Queries¶
Queries addressed to individual stations are in APRS message format (except that they never include a message identifier). The addressee is the callsign of the station being queried.
The message text is the Query Type. This is followed optionally by another callsign — this callsign does not need filler spaces as it is at the end of the data.
Bytes:
| Directed Station Query Format | ||||||
|---|---|---|---|---|---|---|
| : | Addressee | : | ? | Query Type | Callsign of Heard Station | |
| 1 | 9 | 1 | 1 | 5 | 0-9 | |
| Examples Query Typical Response :KH2Z˽˽˽˽˽:?APRSD :N8UR˽˽˽˽˽:Directs=˽WA1LOU˽WD5IVD… A query asking KH2Z what stations he has heard direct. :KH2Z˽˽˽˽˽:?APRSHN0QBF :N8UR˽˽˽˽˽:N0QBF˽HEARD:˽1˽3˽2˽. ˽. ˽4˽5˽6 A query asking for the number of times N0QBF was heard in each of the last 8 hours. (Note the trailing spaces in the callsign following APRSH, padding the callsign to 9 characters). :KH2Z˽˽˽˽˽:?APRSM :N8UR˽˽˽˽˽:Testing{003 A query asking KH2Z for any unacknowledged or undelivered messages for him. KH2Z responds with all such messages. :KH2Z˽˽˽˽˽:?APRSO ;LEADER˽˽˽*092345z4903.50N/07201.75W> A query asking for KH2Z’s APRS Objects. :KH2Z˽˽˽˽˽:?APRSP /092345z4903.50N/07201.75W> A query asking for KH2Z’s position. :KH2Z˽˽˽˽˽:?APRSS >092345zNet Control Center A query asking for KH2Z’s status. :KH2Z˽˽˽˽˽:?APRST :N8UR˽˽˽˽˽:KH2Z>APxxxx,DIGI1,WIDE*: A query asking KH2Z for a trace of the route taken to reach him. :KH2Z˽˽˽˽˽:?PING? :N8UR˽˽˽˽˽:KH2Z>APxxxx,DIGI1,WIDE*: The same query, using PING instead of APRST. |