Fix several bugs in input/output fromat

Thanks to vk1et for these.

1) Correct for additional timestamp langth in raw output buffer when
using mlat mode

2) Don't output a timestamp when the message has been received from a
remote site (the internet). This is to avoid upsetting MLAT because
there is an indeterminate delay between reception at the remote site and
subsequent message arrival in the local dump1090 instance.

3) Allow @ character for raw data input with timestamp, and correctly
calculate the length.

dump1090.c

@@ -56,7 +56,7 @@
 // MinorVer changes when additional features are added, but not for bug fixes (range 00-99)
 // DayDate & Year changes for all changes, including for bug fixes. It represent the release date of the update
 //
-#define MODES_DUMP1090_VERSION     "1.01.1924.13"
+#define MODES_DUMP1090_VERSION     "1.01.2004.13"
 
 #define MODES_DEFAULT_RATE         2000000
 #define MODES_DEFAULT_FREQ         1090000000
@@ -2265,6 +2265,7 @@ void modesSendRawOutput(struct modesMessage *mm) {
             sprintf(p, "%02X", pTimeStamp[j]);
             p += 2;
         }
+    Modes.rawOutUsed += 12; // additional 12 characters for timestamp
     } else
         *p++ = '*';
 
@@ -2307,6 +2308,8 @@ void modesSendSBSOutput(struct modesMessage *mm, struct aircraft *a) {
     // ICAO address of the aircraft
     pCommon += sprintf(pCommon, "111,11111,%02X%02X%02X,111111,", mm->aa1, mm->aa2, mm->aa3); 
 
+    // Make sure the records' timestamp is valid before outputing it
+    if (mm->timestampMsg != (uint64_t)(-1)) {
         // Do the records' time and date now
         epocTime = Modes.stSystemTimeBlk;                         // This is the time of the start of the Block we're processing
         offset   = (int) (mm->timestampMsg - Modes.timestampBlk); // This is the time (in 12Mhz ticks) into the Block
@@ -2317,6 +2320,9 @@ void modesSendSBSOutput(struct modesMessage *mm, struct aircraft *a) {
         stTime   = *localtime(&epocTime.time);                    // convert the time to year, month  day, hours, min, sec
         pCommon += sprintf(pCommon, "%04d/%02d/%02d,", (stTime.tm_year+1900),(stTime.tm_mon+1), stTime.tm_mday); 
         pCommon += sprintf(pCommon, "%02d:%02d:%02d.%03d,", stTime.tm_hour, stTime.tm_min, stTime.tm_sec, epocTime.millitm); 
+    } else {
+        pCommon += sprintf(pCommon, ",,");
+    }  
 
     // Do the current time and date now
     ftime(&epocTime);                                         // get the current system time & date
@@ -2402,8 +2408,12 @@ int decodeHexMessage(struct client *c) {
     }
 
     /* Turn the message into binary. */
-    if (l < 2 || hex[0] != '*' || hex[l-1] != ';') return 0;
+    if (l < 2 || (hex[0] != '*' && hex[0] != '@') || hex[l-1] != ';') return 0;
-    hex++; l-=2; /* Skip * and ; */
+    if (hex[0] == '@') {
+        hex += 13; l -= 15; // Skip @, and timestamp, and ;
+    } else {
+        hex++; l-=2; // Skip * and ;
+    }
     if (l > MODES_LONG_MSG_BYTES*2) return 0; /* Too long message... broken. */
     for (j = 0; j < l; j += 2) {
         int high = hexDigitVal(hex[j]);
@@ -2412,6 +2422,10 @@ int decodeHexMessage(struct client *c) {
         if (high == -1 || low == -1) return 0;
         msg[j/2] = (high<<4) | low;
     }
+    // Always mark the timestamp as invalid for packets received over the internet
+    // Mixing of data from two or more different receivers and publishing
+    // as coming from one would lead to corrupt mlat data
+    // Non timemarked internet data has indeterminate delay
     mm.timestampMsg = -1;
     mm.signalLevel  = -1;
     decodeModesMessage(&mm,msg);