Update gps_client.py return -1 if no socket

gps_client.py

@@ -11,29 +11,28 @@ run this way: python3 example1.py.txt
 import gps               # the gpsd interface module
 import time
 
-session = gps.gps(mode=gps.WATCH_ENABLE)
-
-start = time.perf_counter()
-
 mode = -1    
-
 lat = 0    
-
 lon = 0    
-
 alt = 0
 
 try:
+    
+    session = gps.gps(mode=gps.WATCH_ENABLE)
+    
+    start = time.perf_counter()
+    
+    try:
         while (session.read() == 0) and ((time.perf_counter() - start) < 2) and (mode < 2):
-#        print(gps.MODE_SET)
+    #        print(gps.MODE_SET)
      #       print(session.valid)
             if (session.valid):
                 # not useful, probably not a TPV message
-#            continue
+    #            continue
     
-#        print('Mode: %s(%d) Time: ' %
+    #        print('Mode: %s(%d) Time: ' %
-#              (("Invalid", "NO_FIX", "2D", "3D")[session.fix.mode],
+    #              (("Invalid", "NO_FIX", "2D", "3D")[session.fix.mode],
-#               session.fix.mode), end="")
+    #               session.fix.mode), end="")
             # print time, if we have it
                 print("%d " % session.fix.mode, end="")
                 if (session.fix.mode > mode):
@@ -52,14 +51,14 @@ try:
                 print("%.6f %.6f %.6f" %
                           (session.fix.latitude, session.fix.longitude, session.fix.altitude))
                
-#            else:
+    #            else:
-#                print(" 0 0 0")
+    #                print(" 0 0 0")
     
-except KeyboardInterrupt:
+    except KeyboardInterrupt:
         # got a ^C.  Say bye, bye
         print('')
     
-# Got ^C, or fell out of the loop.  Cleanup, and leave.
+    # Got ^C, or fell out of the loop.  Cleanup, and leave.
-session.close()
+    session.close()
 print("%d %.6f %.6f %.1f" % (mode, lat, lon, alt))
 exit(0)