Falls off network (“Destination host unreachable”)

Question

I am running my Pi headlessly, connecting via SSH over the network. I am having a problem that I can consistently reproduce. I will leave a Python script running on my Pi and come back a few hours later and SSH connections to the Pi will time out.

If I ping it I get the following:

C:\Users\andrew>ping 192.168.1.42

Pinging 192.168.1.42 with 32 bytes of data:
Reply from 192.168.1.46: Destination host unreachable.

The only way I can get it back on the network is to restart it (pull out the power).

Has anyone experienced this? Are there any log files I can look at to diagnose the issue?

Answer 1

It is common for a router to disconnect inactive clients to free up router resources. This can happen at random times if the client has not been active.

Answer 2

I have the same problem I have resorted to pinging my router and if no response, I reboot.

Here is my code. It's a process that reads from a Xbee radio, logs the data and every 10 minutes it Tails the log file and uploads it to my server.

I need to to run unattended 24/365.

The following code runs when the system is started and runs as Root.

For some reason, I think Python kills the network AND ttyUSB0.

The climate monitor runs 24/365 and broadcasts Temp / Humidity every minute.

#!   /usr/bin/python3.2
import os

import serial

import time

from ftplib import FTP

import string

import re




ser = serial.Serial('/dev/ttyUSB0',timeout=600)

ser.open()

print("Starting Climate Sensor Logger\n\r")

linectr = 0

while 1:


    data = ser.readline()

    if (len(data) == 0) :
           os.system('reboot -n')


    # remove embedded nulls
    data = data.translate(None, '\0\n\r')

    tm = time.strftime('%x %X %p')

    ln = tm + " " + data  + "\r\n"
print ln 

    fo = open("Web.txt","a")
fo.write(ln);
    fo.close()

    linectr += 1

    if linectr > 29:


           linectr = 0

           # open raw input file and count lines

           counter = 0
           counter2 = 0

           print("Processing Climate measurements")
           f = open("Web.txt")
           for line in f:
                   counter += 1
           f.close()
           # tail 4320 lines (1440 readings)

           f = open ("Web.txt")
           if counter > 4320:
                   counter -= 4320
                   for line in f:
                           counter2 += 1
                           if counter2 > counter:
                                   break


           # write remainder of file to output with XML header



           fo = open ("out.txt","w")
           fo.write("<?xml version=""1.0"" encoding=""UTF-8)"" ?>\r")


           # clean up lines for Javascript

           for line in f:
                   line = line.replace("\0","")
                   line = line.replace("\n","")
                   line = line + "\r"

                   # write tail 4320 readings
                   fo.write(line)

           f.close()
           fo.close()

           # Ready to upload to web server

           try:

                 print("Uploading file to web server")


                 fl = open("Upload.log","a")
                 ln = "\r\nAttempting Upload at :" + tm + " "
                 fl.write(ln)
                 print("Ping Router")

                 ret = os.system("ping -c 3 -W 1000 192.168.0.1")
                 if ret != 0:
                     print "Network is down"
                     fl.write("Network down, Reboot")
                     fl.close()
                     os.system('reboot -n')

                 print("Network is up")

                 fl.write("Network OK")
                 fl.close()

                 ftp = FTP('pcranwell.com');

                 ftp.login('userid','password');

                 file = open('out.txt','rb');

                 ftp.cwd('public_html/PB/data');
                 ftp.storbinary('STOR ' + 'Web.txt', open('out.txt', 'rb'));
                 ftp.close();



                 print("FTP transfer finished")
           except:
                 print("Transfer Failed")        

           finally:
                 print("Continue")