Hostname issue.

Fergus,

Where are you running the socket.gethostbyaddr('10.0.128.2') from ?  The Pi itself, another different Pi, a Windows machine ?

There are many different ways of resolving a hostname, DNS, mDNS, WINS, NetBIOS broadcast, /etc/hosts static entries, NIS/YP etc.  You'd need to make sure that the Pi and the other systems are all using the same method and that the method you pick actually works for local names.

What happens behind the gethostbyaddr call is often complex. On a linux machine you can look in /etc/nsswitch.conf for a line starting with hosts: everything after that on the same line are different places that will be queried for a name. However it doesn't end there. Say you have:

hosts:     files     dns     winbind

files says to look in /etc/hosts

dns says to query a dns server as defined in /etc/resolv.conf, perhaps with a search order defined in the file

winbind is a daemon (part of samba) that can lookup name details from windows and would need configured in /etc/smb.conf

as the available methods are plugins to glibc there could be many more available (ls /lib/libnss*.so on your Pi for a list of possible methods).

You could also be missing a service like avahi on the linux side or bonjour on windows that would help solve your problem. As someone on the other forum points out, maybe your friends router is helping out somewhere, have you tried your RPi on his network ?  Or his on your network ?

If you're interested in digging into the details, get a copy of wireshark and do a packet trace of what happens when your script runs the gethostbyaddr call. Knowing how the lookup is being done may well help point you in the right direction.

I have decided to add a check into my python script without using hostnames as that was tempramental.

Here is an extract:

try:

    robot_detection = raw_input("Which Robot do you wish to control? (overwatch = '1' / recon = '2' / butterfly = '3'): ")

   

    while robot_detection != '1' or robot_detection != '2' or robot_detection == '3':

        if robot_detection == '3':

            print 'Support for CMDbutterfly will be coming in a later release.  Please select another option from the ones provided. '

        elif robot_detection == '1' or robot_detection == '2':

            break

        else:

            print 'Enter a valid value! '

        robot_detection = raw_input("Which Robot do you wish to control? (overwatch = '1' / recon = '2' / butterfly = '3'): ")

       

       

    if robot_detection == '1':

        robot_detection = 'CMDoverwatch'

    elif robot_detection == '2':

        robot_detection = 'CMDrecon'

    print " "

    print  "Controlling " +robot_detection

    print " "

This way you don't need to check because the user has told it.

On the Pi:

sudo apt-get avahi-daemon

Then any other Linux box running avahi or Apple computer running Bonjour (which I think it includes as its zeroconfig) or if you install Bonjour on Windows, they should all be able to find your Raspberry Pi by the name CMDoverwatch.local, at least for things like ping and ssh.  If you want other services available, you have to figure out what to put in /etc/avahi/services.

[code]efflandt@XPS8100-1204:~$ ping -c4 raspberrypi.local

PING raspberrypi.local (192.168.1.106) 56(84) bytes of data.

64 bytes from raspberrypi.local (192.168.1.106): icmp_req=1 ttl=64 time=10.7 ms

64 bytes from raspberrypi.local (192.168.1.106): icmp_req=2 ttl=64 time=20.3 ms

64 bytes from raspberrypi.local (192.168.1.106): icmp_req=3 ttl=64 time=45.2 ms

64 bytes from raspberrypi.local (192.168.1.106): icmp_req=4 ttl=64 time=65.4 ms

--- raspberrypi.local ping statistics ---

4 packets transmitted, 4 received, 0% packet loss, time 3001ms

rtt min/avg/max/mdev = 10.710/35.441/65.435/21.418 ms

efflandt@XPS8100-1204:~$ ssh raspberrypi.local

Linux raspberrypi 3.2.27+ #250 PREEMPT Thu Oct 18 19:03:02 BST 2012 armv6l

The programs included with the Debian GNU/Linux system are free software;

the exact distribution terms for each program are described in the

individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent

permitted by applicable law.

Last login: Sat Dec 15 01:09:23 2012 from xps8100-1204.local[/code]

And avahi name resolution works as well for a python script sending its status to an Ubuntu box to monitor how long a battery pack lasts (maybe not optimum code, but I am new at python, and not sure if code tags work here to show indents).  I did not need anything in /etc/avahi/services for this, just a python script constantly listening on this port on the server:

[code]#!/usr/bin/python

# client to send uptime to network monitor

import socket

import os

import time

import math

# hostname.local is if pimon.py server is running avahi or Bonjour

HOST = 'xps8100-1204.local'  # remote IP resolvable hostname

PORT = 53142                 # same port used by server

rfPath = "/proc/uptime"

try:

    while 1:

        r = open(rfPath, 'r')

        uptime = r.readline()

        r.close()

        # split out first number in line as float

        uptime = float((uptime.split())[0])

        # typical Linux like date

        current_time = time.strftime("%a %b %d %X %Z %Y", time.localtime())

        # from total sec, figure strings for hrs and 2 digit min, sec

        sec, min = math.modf(uptime / 60)

        #s = str(int(round(sec * 60,0))).zfill(2)

        min, hr = math.modf(min / 60)

        m = str(int(min * 60)).zfill(2)

        if hr > 23:

            hr, days = math.modf(hr / 24)

            h = str(int(hr * 24)).zfill(1)

            d = str(int(days))

            if days > 1 : day = 'days'

            else: day = 'day'

            output = "{} up {} {}, {}:{} hrs".format(current_time, d, day, h, m)

        else:

            h = str(int(hr)).zfill(1)

            output = "{} up {}:{} hrs".format(current_time, h, m)

        # send data and print confirmation response

        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

        s.connect((HOST, PORT))

        s.sendall(output)

        data = s.recv(1024)

        s.close()

        print 'Received', repr(data)

        # sleep: 60 = 1 min, 300 = 5 min, 900 = 15 min, 1800 = 30 min, 3600 = 1 hr

        try:

            time.sleep(300)

        except KeyboardInterrupt:

            break

    # loop until Ctrl+C

except KeyboardInterrupt:

    pass[/code]

Report on receiving end so far from Pi on battery pack:

Connected by ('192.168.1.106', 60677)

Sat Dec 15 07:40:51 CST 2012 up 7:27 hrs

Well, I  have no answer but I need to learn about this stuff, so I have a question ....

If your router is set to 192.168.1.1, with a subnet mask of 255.255.255.255.0 , why would you put your peripheral devices on a different subnet (10.0.128.100)?

Would you expect to be able to ping them?

This is a *genuine* question from a relative novice.

--G

I think you might be confused.

I wanted to have a portable network set-up using the 10.0.128.100 IP address.

My Personal Home network uses 192.168.*.*  (removed numbers)

I am talking about two network situations where the devices are in separate situations.

About your question:

Would you expect to be able to ping them?

Yes.  Provided you have put the same subnet mask on both devices.  I have seen this done on Corperate networks where they use an IP address for wireless devices and LAN devices. 

Cian

I think you'll find they add a route to allow the different IP address to work, or they use NAT (Network Address Translation) which is effectively what your broadband router does.

This may be part of the switch, or within the devices protocols.

Normally you will have a gateway address, where the device heads if its not an address on the local LAN.

For grahame's example there are 254 address's available, so anything that is 192.168.1. x will be treated as Local, and anything else heads out the gateway and is resolved elsewhere.

If I understand correctly you have a portable network that is attached onto your home network.

Have you tried changing the Gateway address to the 192.168.*.* (pick something that doesn't clash).

This would then mean that anything not intended to be local (ie 10.0.128. x) will go out the gateway which should be your local lan.

Mark

Cian,

You need to bridge the two networks together, both the 192 and 10 networks are reserved for internal networking. These will be the internal addresses on your own network, not the outward facing IP assigned by your ISP.

Putting the same netmask will not cause them to be linked, as Mark indicates this is only in reference to the number of ip address available on that subnet. See below, I think it will give you some pointers.

http://serverfault.com/questions/198419/how-to-bridge-networks-192-168-191-0-24-and-10-9-0-0-16

Steve

I wasn't confused Cian, so much as curious. Thanks for explaining about your two networks. The comments above seem to be well in line with my own humble thinking, and will hopefully help you reach your goal.

--G

P.S.

Since you know the IPs on your alternative network -- I imagine that you use Address Reservation or no DHCP -- it should be very simple to access them  that way. Interested to know the advantage(s) of calling them by name (lots to learn, here).

--G

I was curious, and cautiously so, to know what would happen if one sends an IP request 'intended' for local receipt out onto the internet, so I did a whois on    10.0.128.100   and got this....

NetRange:       10.0.0.0 - 10.255.255.255

CIDR:           10.0.0.0/8

OriginAS:      

NetName:        PRIVATE-ADDRESS-ABLK-RFC1918-IANA-RESERVED

NetHandle:      NET-10-0-0-0-1

Parent:        

NetType:        IANA Special Use

RegDate:       

Updated:        2011-04-12

Ref:            http://whois.arin.net/rest/net/NET-10-0-0-0-1

OrgName:        Internet Assigned Numbers Authority

OrgId:          IANA

Address:        12025 Waterfront Drive

Address:        Suite 300

City:           Los Angeles

StateProv:      CA

PostalCode:     90292

Country:        US

RegDate:       

Updated:        2012-08-31

I suppose it doesn't matter much, and they might blame the Albanians anyway, according to your info.

--G