// readMsgFromSocket will pull basestation (and extended basestation)
// formatted messages from the socket, and send them down the channel.
// It will retry the connection on failure.
func readMsgFromSocket(wg *sync.WaitGroup, hostport string, msgChan chan<- *adsb.Msg) {
nTimeMismatches := 0
lastBackoff := time.Second
wg.Add(1)
outerLoop:
for {
if weAreDone() {
break
} // outer
conn, err := net.Dial("tcp", hostport)
if err != nil {
Log.Printf("connect '%s': err %s; trying again in %s ...", hostport, err, lastBackoff*2)
time.Sleep(lastBackoff)
if lastBackoff < time.Minute*5 {
lastBackoff *= 2
}
continue
}
lastBackoff = time.Second
Log.Printf("connected to '%s'", hostport)
// a net.Conn implements io.Reader
scanner := bufio.NewScanner(conn)
for scanner.Scan() { // This can block indefinitely ...
if weAreDone() {
break outerLoop
}
if err := scanner.Err(); err != nil {
Log.Printf("killing connection, scanner err: %v\n", err)
conn.Close()
break // inner
}
msg := adsb.Msg{}
text := scanner.Text()
if err := msg.FromSBS1(text); err != nil {
Log.Printf("killing connection, SBS input:%q, parse fail: %v", text, err)
break // inner
}
// If there is significant clock skew, we should bail. But, it seems
// that sometimes we pick up stale data from dump1090; so wait to see
// if it passes.
offset := time.Since(msg.GeneratedTimestampUTC)
if offset > time.Minute*30 || offset < time.Minute*-30 {
nTimeMismatches++
if nTimeMismatches < 100 {
continue // do not process this message
} else {
Log.Fatalf("100 bad msgs; set -timeloc ?\nNow = %s\nmsg = %s\n", time.Now(),
msg.GeneratedTimestampUTC)
}
}
// If the message is flagged as one we should mask, honor that
if msg.IsMasked() {
continue
}
msgChan <- &msg
}
}
wg.Done()
Log.Printf(" ---- readMsgFromSocket, clean shutdown\n")
}
