Improve compatibility with megastek devices

Megastek devices send some data which either is not
fully compliant with the megastek protocol (by omitting
some data) or which is (for our purposes) garbage data,
which is only delimited with a single LF (0x0A).

1 files changed, 19 insertions, 14 deletions

diff --git a/src/main/java/org/traccar/protocol/MegastekProtocolDecoder.java b/src/main/java/org/traccar/protocol/MegastekProtocolDecoder.java
index f0c0df8a6..2ce5b9dae 100644
--- a/src/main/java/org/traccar/protocol/MegastekProtocolDecoder.java
+++ b/src/main/java/org/traccar/protocol/MegastekProtocolDecoder.java
@@ -141,6 +141,9 @@ public class MegastekProtocolDecoder extends BaseProtocolDecoder {
 
             beginIndex = endIndex + 2;
             endIndex = sentence.indexOf('*', beginIndex) + 3;
+            if (beginIndex > endIndex) {
+                return null;
+            }
             location = sentence.substring(beginIndex, endIndex);
 
             beginIndex = endIndex + 1;
@@ -243,13 +246,13 @@ public class MegastekProtocolDecoder extends BaseProtocolDecoder {
             .number("dd,")
             .number("(dd),")                     // satellites
             .number("dd,")
-            .number("(d+.d+),")                  // hdop
+            .number("(d+.d+)?,")                 // hdop
             .number("(d+.d+)?,")                 // speed
             .number("(d+.d+)?,")                 // course
             .number("(-?d+.d+)?,")               // altitude
             .number("(d+.d+)?,")                 // odometer
-            .number("(d+),")                     // mcc
-            .number("(d+),")                     // mnc
+            .number("(d+)?,")                    // mcc
+            .number("(d+)?,")                    // mnc
             .number("(xxxx)?,")                  // lac
             .number("(x+)?,")                    // cid
             .number("(d+)?,")                    // gsm
@@ -276,7 +279,7 @@ public class MegastekProtocolDecoder extends BaseProtocolDecoder {
             .groupEnd("?").text(",")
             .number("(d+)?,")                    // rfid
             .number("([01])(d)?").optional()     // charge and belt status
-            .expression("[^,]*,").optional()
+            .expression("[^,]*,")
             .number("(d+)?,")                    // battery
             .expression("([^,]*)[,;]")           // alert
             .any()
@@ -318,17 +321,19 @@ public class MegastekProtocolDecoder extends BaseProtocolDecoder {
             position.set(Position.KEY_ODOMETER, parser.nextDouble(0) * 1000);
         }
 
-        int mcc = parser.nextInt();
-        int mnc = parser.nextInt();
-        Integer lac = parser.nextHexInt();
-        Integer cid = parser.nextHexInt();
-        Integer rssi = parser.nextInt();
-        if (lac != null && cid != null) {
-            CellTower tower = CellTower.from(mcc, mnc, lac, cid);
-            if (rssi != null) {
-                tower.setSignalStrength(rssi);
+        if (parser.hasNext(5)) {
+            int mcc = parser.nextInt();
+            int mnc = parser.nextInt();
+            Integer lac = parser.nextHexInt();
+            Integer cid = parser.nextHexInt();
+            Integer rssi = parser.nextInt();
+            if (lac != null && cid != null) {
+                CellTower tower = CellTower.from(mcc, mnc, lac, cid);
+                if (rssi != null) {
+                    tower.setSignalStrength(rssi);
+                }
+                position.setNetwork(new Network(tower));
             }
-            position.setNetwork(new Network(tower));
         }
 
         if (parser.hasNext(5)) {