gpsd python client

Question

I'm trying to write a very simple python client for Gpsd, but I have this error after some time of execute the script:

Traceback (most recent call last):
 File "gps_cap.py", line 13, in <module>
   g.stream()
 File "/usr/lib/python2.6/site-packages/gps/gps.py", line 348, in stream
   gpsjson.stream(self, flags)
 File "/usr/lib/python2.6/site-packages/gps/client.py", line 176, in stream
   return self.send(arg + "}")
 File "/usr/lib/python2.6/site-packages/gps/client.py", line 111, in send
   self.sock.send(commands)
socket.error: [Errno 104] Connection reset by peer

and this is my python code:

import os
from gps import *
from time import *

g = gps(mode=WATCH_ENABLE)
while 1:
      os.system('clear')
       g.poll()
       if PACKET_SET:
               g.stream()

       print
       print ' GPS reading'
       print '----------------------------------------'
       print 'latitude    ' , g.fix.latitude
       print 'longitude   ' , g.fix.longitude
       print 'time utc    ' , g.utc,' + ', g.fix.time
       print 'altitude    ' , g.fix.altitude
       print 'epc         ' , g.fix.epc
       print 'epd         ' , g.fix.epd
       print 'eps         ' , g.fix.eps
       print 'epx         ' , g.fix.epx
       print 'epv         ' , g.fix.epv
       print 'ept         ' , g.fix.ept
       print 'speed       ' , g.fix.speed
       print 'climb       ' , g.fix.climb
       print 'track       ' , g.fix.track
       print 'mode        ' , g.fix.mode
       print
       print 'sats        ' , g.satellites

       sleep(1)

Maybe anyone can help with this issue? I'm runnig Gpsd 2.95 in a ArchLinux box.

Thanks!

Answer 1

To keep an old question alive, pasted below is the current state of GPS3, a Python 2.7-3.5 gpsd client found at https://github.com/wadda/gps3.

GPS3 has two components; the GPSDSocket class, and the Fix class.

GPSD delivers JSON data in a number of 'classes', TPV, SKY, etc. After connecting to the GPSD, GPS3 unpacks those JSON objects into dictionaries (Fix.TPV['lat'], Fix.SKY['satellites'], etc.)

Common use would create an instance, e.g., fix = gps3.Fix(), and all available data would be derived from the name of the native JSON object (e.g., fix.TPV['speed'], fix.TPV['alt'], etc.)

Confer usage with a demo application gegps3.py which creates a kml file (/tmp/gps3_live.kml) to be viewed in Google Earth.

#!/usr/bin/env python3
# coding=utf-8
"""
GPS3 (gps3.py) is a Python 2.7-3.5 GPSD interface (http://www.catb.org/gpsd)
Defaults host='127.0.0.1', port=2947, gpsd_protocol='json'

GPS3 has two classes.
1) 'GPSDSocket' to create a GPSD socket connection and request/retreive GPSD output.
2) 'Fix' unpacks the streamed gpsd data into python dictionaries.

These dictionaries are literated from the JSON data packet sent from the GPSD.

Import           import gps3
Instantiate      gps_connection = gps3.GPSDSocket(host='192.168.0.4')
                 gps_fix = gps3.Fix()
Iterate          for new_data in gps_connection:
                     if new_data:
                        gps_fix.refresh(new_data)
Use                     print('Altitude = ',gps_fix.TPV['alt'])
                        print('Latitude = ',gps_fix.TPV['lat'])

Consult Lines 152-ff for Attribute/Key possibilities.
or http://www.catb.org/gpsd/gpsd_json.html

Run human.py; python[X] human.py [arguments] for a human experience.
"""
from __future__ import print_function

import json
import select
import socket
import sys

__author__ = 'Moe'
__copyright__ = 'Copyright 2015-2016  Moe'
__license__ = 'MIT'
__version__ = '0.2'

HOST = '127.0.0.1'  # gpsd
GPSD_PORT = 2947  # defaults
PROTOCOL = 'json'  # "


class GPSDSocket(object):
    """Establish a socket with gpsd, by which to send commands and receive data."""

    def __init__(self, host=HOST, port=GPSD_PORT, gpsd_protocol=PROTOCOL, devicepath=None):
        self.devicepath_alternate = devicepath
        self.response = None
        self.protocol = gpsd_protocol
        self.streamSock = None

        if host:
            self.connect(host, port)

    def connect(self, host, port):
        """Connect to a host on a given port.
        Arguments:
            port: default port=2947
            host: default host='127.0.0.1'
        """
        for alotta_stuff in socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM):
            family, socktype, proto, _canonname, host_port = alotta_stuff
            try:
                self.streamSock = socket.socket(family, socktype, proto)
                self.streamSock.connect(host_port)
                self.streamSock.setblocking(False)
                self.watch(gpsd_protocol=self.protocol)
            except OSError as error:
                sys.stderr.write('\nGPSDSocket.connect OSError is-->', error)
                sys.stderr.write('\nAttempt to connect to a gpsd at {0} on port \'{1}\' failed:\n'.format(host, port))
                sys.exit(1)  # TODO: gpsd existence check and start

    def watch(self, enable=True, gpsd_protocol='json', devicepath=None):
        """watch gpsd in various gpsd_protocols or devices.
        Arguments:
            self:
            enable: (bool) stream data to socket
            gpsd_protocol: (str) 'json' | 'nmea' | 'rare' | 'raw' | 'scaled' | 'split24' | 'pps'
            devicepath: (str) device path - '/dev/ttyUSBn' for some number n or '/dev/whatever_works'
        Returns:
            command: (str) e.g., '?WATCH={"enable":true,"json":true};'
        """
        # N.B.: 'timing' requires special attention, as it is undocumented and lives with dragons.
        command = '?WATCH={{"enable":true,"{0}":true}}'.format(gpsd_protocol)

        if gpsd_protocol == 'rare':  # 1 for a channel, gpsd reports the unprocessed NMEA or AIVDM data stream
            command = command.replace('"rare":true', '"raw":1')
        if gpsd_protocol == 'raw':  # 2 channel that processes binary data, received data verbatim without hex-dumping.
            command = command.replace('"raw":true', '"raw",2')
        if not enable:
            command = command.replace('true', 'false')  # sets -all- command values false .
        if devicepath:
            command = command.replace('}', ',"device":"') + devicepath + '"}'

        return self.send(command)

    def send(self, commands):
        """Ship commands to the daemon
        Arguments:
            commands: e.g., '?WATCH={{'enable':true,'json':true}}'|'?VERSION;'|'?DEVICES;'|'?DEVICE;'|'?POLL;'
        """
        # The POLL command requests data from the last-seen fixes on all active GPS devices.
        # Devices must previously have been activated by ?WATCH to be pollable.
        if sys.version_info[0] < 3:  # Not less than 3, but 'broken hearted' because
            self.streamSock.send(commands)  # 2.7 chokes on 'bytes' and 'encoding='
        else:
            self.streamSock.send(bytes(commands, encoding='utf-8'))  # It craps out here when there is no gpsd running
            # TODO: Add recovery, check gpsd existence, re/start, etc..

    def __iter__(self):
        """banana"""  # <------- for scale
        return self

    def next(self, timeout=0):
        """Return empty unless new data is ready for the client.
        Arguments:
            timeout: Default timeout=0  range zero to float specifies a time-out as a floating point
        number in seconds.  Will sit and wait for timeout seconds.  When the timeout argument is omitted
        the function blocks until at least one file descriptor is ready. A time-out value of zero specifies
        a poll and never blocks.
        """
        try:
            waitin, _waitout, _waiterror = select.select((self.streamSock,), (), (), timeout)
            if not waitin: return
            else:
                gpsd_response = self.streamSock.makefile()  # '.makefile(buffering=4096)' In strictly Python3
                self.response = gpsd_response.readline()
            return self.response

        except OSError as error:
            sys.stderr.write('The readline OSError in GPSDSocket.next is this: ', error)

    __next__ = next  # Workaround for changes in iterating between Python 2.7 and 3

    def close(self):
        """turn off stream and close socket"""
        if self.streamSock:
            self.watch(enable=False)
            self.streamSock.close()
        self.streamSock = None


class Fix(object):
    """Retrieve JSON Object(s) from GPSDSocket and unpack it into respective
    gpsd 'class' dictionaries, TPV, SKY, etc. yielding hours of fun and entertainment.
    """

    def __init__(self):
        """Potential data packages from gpsd for a generator of class attribute dictionaries"""

        packages = {'VERSION': {'release', 'proto_major', 'proto_minor', 'remote', 'rev'},
                    'TPV': {'alt', 'climb', 'device', 'epc', 'epd', 'eps', 'ept', 'epv', 'epx', 'epy', 'lat', 'lon', 'mode', 'speed', 'tag', 'time', 'track'},
                    'SKY': {'satellites', 'gdop', 'hdop', 'pdop', 'tdop', 'vdop', 'xdop', 'ydop'},
                    # Subset of SKY: 'satellites': {'PRN', 'ss', 'el', 'az', 'used'}  # is always present.
                    'GST': {'alt', 'device', 'lat', 'lon', 'major', 'minor', 'orient', 'rms', 'time'},
                    'ATT': {'acc_len', 'acc_x', 'acc_y', 'acc_z', 'depth', 'device', 'dip', 'gyro_x', 'gyro_y', 'heading', 'mag_len', 'mag_st', 'mag_x',
                            'mag_y', 'mag_z', 'pitch', 'pitch_st', 'roll', 'roll_st', 'temperature', 'time', 'yaw', 'yaw_st'},
                    # 'POLL': {'active', 'tpv', 'sky', 'time'},
                    'PPS': {'device', 'clock_sec', 'clock_nsec', 'real_sec', 'real_nsec', 'precision'},
                    'TOFF': {'device', 'clock_sec', 'clock_nsec','real_sec', 'real_nsec' },
                    'DEVICES': {'devices', 'remote'},
                    'DEVICE': {'activated', 'bps', 'cycle', 'mincycle', 'driver', 'flags', 'native', 'parity', 'path', 'stopbits', 'subtype'},
                    # 'AIS': {}  # see: http://catb.org/gpsd/AIVDM.html
                    'ERROR': {'message'}}  # TODO: Full suite of possible GPSD output

        for package_name, dataset in packages.items():
            _emptydict = {key: 'n/a' for key in dataset}
            setattr(self, package_name, _emptydict)

        self.DEVICES['devices'] = {key: 'n/a' for key in packages['DEVICE']}  # How does multiple listed devices work?
        # self.POLL = {'tpv': self.TPV, 'sky': self.SKY, 'time': 'n/a', 'active': 'n/a'}

    def refresh(self, gpsd_data_package):
        """Sets new socket data as Fix attributes in those initialied dictionaries
        Arguments:
            self:
            gpsd_data_package (json object):
        Provides:
        self attribute dictionaries, e.g., self.TPV['lat'], self.SKY['gdop']
        Raises:
        AttributeError: 'str' object has no attribute 'keys' when the device falls out of the system
        ValueError, KeyError: most likely extra, or mangled JSON data, should not happen, but that
        applies to a lot of things.
        """
        try:
            fresh_data = json.loads(gpsd_data_package)  # The reserved word 'class' is popped from JSON object class
            package_name = fresh_data.pop('class', 'ERROR')  # gpsd data package errors are also 'ERROR'.
            package = getattr(self, package_name, package_name)  # packages are named for JSON object class
            for key in package.keys():  # TODO: Rollover and retry.  It fails here when device disappears
                package[key] = fresh_data.get(key, 'n/a')  # Updates and restores 'n/a' if key is absent in the socket
                # response, present --> 'key: 'n/a'' instead.'
        except AttributeError:  # 'str' object has no attribute 'keys'
            print('No Data')
            return

        except (ValueError, KeyError) as error:
            sys.stderr.write(str(error))  # Look for extra data in stream
            return


if __name__ == '__main__':
    print('\n', __doc__)

#
# Someday a cleaner Python interface will live here
#
# End

Answer 2

I know this question is pretty old but i still drop my answer here in case someone needs it in the future:

#! /usr/bin/python
# Written by Dan Mandle http://dan.mandle.me September 2012
# License: GPL 2.0 
import os
from gps import *
from time import *
import time
import threading

gpsd = None #seting the global variable

os.system('clear') #clear the terminal (optional)

class GpsPoller(threading.Thread):
  def __init__(self):
    threading.Thread.__init__(self)
    global gpsd #bring it in scope
    gpsd = gps(mode=WATCH_ENABLE) #starting the stream of info
    self.current_value = None
    self.running = True #setting the thread running to true

  def run(self):
    global gpsd
    while gpsp.running:
      gpsd.next() #this will continue to loop and grab EACH set of gpsd info to clear the buffer

if __name__ == '__main__':
  gpsp = GpsPoller() # create the thread
  try:
    gpsp.start() # start it up
    while True:
      #It may take a second or two to get good data
      #print gpsd.fix.latitude,', ',gpsd.fix.longitude,'  Time: ',gpsd.utc

      os.system('clear')

      print
      print ' GPS reading'
      print '----------------------------------------'
      print 'latitude    ' , gpsd.fix.latitude
      print 'longitude   ' , gpsd.fix.longitude
      print 'time utc    ' , gpsd.utc,' + ', gpsd.fix.time
      print 'altitude (m)' , gpsd.fix.altitude
      print 'eps         ' , gpsd.fix.eps
      print 'epx         ' , gpsd.fix.epx
      print 'epv         ' , gpsd.fix.epv
      print 'ept         ' , gpsd.fix.ept
      print 'speed (m/s) ' , gpsd.fix.speed
      print 'climb       ' , gpsd.fix.climb
      print 'track       ' , gpsd.fix.track
      print 'mode        ' , gpsd.fix.mode
      print
      print 'sats        ' , gpsd.satellites

      time.sleep(5) #set to whatever

  except (KeyboardInterrupt, SystemExit): #when you press ctrl+c
    print "\nKilling Thread..."
    gpsp.running = False
    gpsp.join() # wait for the thread to finish what it's doing
  print "Done.\nExiting."

This code work with thread and will give out a nice output of gpsd data to the screen. It can be terminated with Ctrl + C.

All credits go to http://www.danmandle.com/blog/getting-gpsd-to-work-with-python/

Answer 3

I would put some money on this snippit from the gpsd how to page; also, thanks for the bootstrap code.

http://gpsd.berlios.de/client-howto.html

If you’re a clever sort, you’re already wondering what the daemon does if the application at the other end of the client socket doesn’t read data out of it as fast as gpsd is shipping it upwards. And the answer is this: eventually the socket buffer fills up, a write from the daemon throws an error, and the daemon shuts down that client socket.

As long as your application checks for and reads socket data no less often than once a second, you won’t — and a second is a lot of time in which to come back around your main loop.