Post APRSParser – A Spring Example included a class, SocketAPRSDataSource, which when coupled with class DataSourceCapture would capture APRS data from and APRS-IS server to a file for playback in later development.

Listing 1 contains a quick Groovy script to do the same thing. It can probably be refined a bit should demonstrate how powerful groovy is for quick prototyping.

Listing 1

/* Open a socket to an APRS-IS server, log in as guest and filter to only receive
 * messages from call signs prefixed with G, M or 2.
 * Write all messages to a file with a time stamp.
 */

def writeLine(writer, line) {
    def date = new Date()
    lineOutput = date.format("yyyy-MM-dd'T'HH:mm:ss,", TimeZone.getTimeZone("UTC")) + line
    println(lineOutput)
    writer.println(lineOutput)
    writer.flush()
}

new File("APRSData.txt").withPrintWriter { writer ->
    // Using a UK server. See http://www.aprs2.net/serverstats.php for other servers.
    s = new Socket("uk.aprs2.net", 14580);
    s.withStreams { input, output ->
        // Wait for the software version line from the server before logging in.
        writeLine(writer, input.newReader().readLine())

        // Identifying software as UI-View32. Would rather not do this but using other
        // strings seems to prevent successful login.
        output << "user Guest pass -1 vers UI-View32 V2.03 filter p/G/M/2\n"

        // Record all lines until program killed or socket closed.
        input.newReader().eachLine { 
            writeLine(writer, it)
        }
    }
}