I wrote this code for finding google ip in python
import socket
print socket.gethostbyname('google.com')
.
.
173.194.39.0
but if we use command prompt and ping command for finding google ip result is:216.58.208.36
why there is difference between two results?
Both of those IP addresses resolve to Google.com. We can verify this from the command line with the unix whois command.
$ whois 216.58.208.36
NetRange: 216.58.192.0 - 216.58.223.255
CIDR: 216.58.192.0/19
NetName: GOOGLE
$ whois 173.194.39.0
NetRange: 173.194.0.0 - 173.194.255.255
CIDR: 173.194.0.0/16
NetName: GOOGLE
I ran into this same issue and the cause was that the first command that required an IP address was using a cached DNS entry (because the DNS entry's time to live (TTL) hadn't expired yet) and then by the time the second command was issued the TTL had expired on the cached entry so a new DNS request was made for the domain therefore grabbing a new IP address from the DNS server which happened to be different because the domain had a lot of IP addresses just like Google.com.
Python just relies on the Operating System's DNS resolver (or whatever daemon is running) and as far as I know the socket module doesn't give you the ability to clear the DNS cache before it tries to resolve an address. If you want more control over this functionality you can use DNSPython or something similar. If you are using a daemon for DNS on your operating system (like on Linux, for example) then usually restarting the daemon will force a flush of DNS cache and you find both addresses to the be same (unless you run into the timing issue as described above with the TTL's expiring).
Hostnames are translated to IP addresses through something called a DNS server. When you type a name into a web browser or use a program such as ping, the hostname that you provide (google.com) eventually reaches an authoritative DNS server for that domain-separate from the server that you correspond with for the actual content.
google.com has multiple different servers that can respond to data requests. Depending on the implementation of the different programs you are using to generate the request and other factors such as the network traffic at the time that you make the request, multiple requests from the same host may be directed to different servers by the authoritative DNS server. This is accomplished by returning different IP addresses to your machine.
FWIW, both ping and socket.gethostbyname() for google.com resolve to 216.58.217.14 on my machine, running OS X Yosemite.
Related
So I'm using socket to connect clients to the server. For that, I need the computer's ip. Currently, the best way I found is this:
socket.gethostbyname(socket.gethostname())
I then use requests to tell my clients about my ip, and they connect. The issue here is that when my vpn is on, I get another host and that causes the clients to be unable to connect.
But when I open command prompt and type ipconfig, I get the correct ip regardless of the vpn status. So I need to get the same ip as would be shown under IPv4 in command prompt, is this possible in python?
I'm trying to get the server to work on any device regardless of exceptions such as this.
Thanks!
The way you retrieve the IP addresses of your system (most systems these days have multiple) uses the hostname of your system and therefore depends on i.e. DNS and your local hosts file. It will only give you one address, and can be quite unreliable, as you have seen with your VPN.
I'd recommend using the netifaces package. With it you can retrieve a list of all network interfaces and all their addresses.
An example from the manual:
>>> addrs = netifaces.ifaddresses('en0')
>>> addrs[netifaces.AF_INET]
[{'broadcast': '10.15.255.255', 'netmask': '255.240.0.0', 'addr': '10.0.1.4'}, {'broadcast': '192.168.0.255', 'addr': '192.168.0.47'}]
You should be able to install it with pip. The source repository is here: https://bitbucket.org/al45tair/netifaces
Yeah so I ran into this issue and it seems that ipconfig command does work, so I used the following. It calls ipconfig using subprocess and uses a regex pattern to match the ipv4 line. Since there's two ipv4 lines, and on my machine the VPN appeared as Unknown adapter WindscribeWireguard: before Wireless LAN adapter Wi-Fi: so I ended up matching the last one that appears. It's possible this isn't robust but I'm sure one of my users will let me know then.
from subprocess import check_output
import re
ipv4_pattern = re.compile(r'IPv4 Address.*:\s*(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})')
def get_ipv4():
ipconfig_output = check_output(['ipconfig'], shell=True, text=True, encoding='iso8859-2')
return ipv4_pattern.findall(ipconfig_output)[-1]
socket.gethostbyname("vidzi.tv") giving '104.20.87.139'
ping vidzi.tv gives '104.20.86.139'
socket.gethostbyname("www.vidzi.tv") giving '104.20.87.139'
ping www.vidzi.tv gives '104.20.86.139'
Why socket.gethostbyname is giving wrong IP for this website? It is giving right IP for other websites?
I don't see any "wrong" IPs in your question. A DNS server is allowed to return multiple IP addresses for the same host. The client generally just picks one of them. A lot of servers use this as a part of their load balancing, as clients select any available server and since they generally would pick different ones the traffic gets split up evenly. Your ping command and your gethostbyname command are just selecting different available IPs, but neither is "wrong".
You can see all the IPs that are returned for a given hostname with a tool like nslookup or dig.
How do force Python to use a specific VPN? The VPNs are configured and listed with ifconfig as ppp0 .. pppn, using PPTP. For a client I need to connect to an arbitrary VPN on a per Python-process basis. I couldn't find any examples on the internet for this use case.
The use case requires that a connection is made to a remote host using a specific IP address (which is on the other end of the VPN).
I am using windows 7 and python 2.7 I created local https server with redirect url to server as its IP address. I created cert file for https using openssl.
Then I mapped my local system IP(172.16.17.84) to myapp.nobies.in in hosts file of windows.
So my server redirect url becomes https://myapp.nobies.in:443.
By doing this IP mapping in host file, I am not getting SSL error.
But, I want to distribute my app to others, so, writing in host file through python code is not desirable, as it needs administrative privileges.
So, is there any way to assign/map this IP with hostname instead of making an entry in hosts file.
Have you considered just creating the certificate for the IP address? That wouldn't be much more fragile (probably less fragile, actually) than having to manually add the domain name to hosts files. See https://stackoverflow.com/a/11710762/138772 and https://stackoverflow.com/a/8444863/372643 for more info on that.
An alternative, but one probably requiring more work, would be to include a local DNS server in your app that redirects the domain name to your IP address. I can't really say what the best one to use for that would be, though.
I am trying to send some traffic via python using scapy (on Ubuntu). I am using a range of source IPs (10.0.0.32/29). Everything seems to be working (at least I see the traffic in wireshark and it reaches my firewall) but I am having a problem completing the TCP handshake using the IP addresses that aren't the main IP of the eth0 adapter. Does anyone know if this is possible to do:
Source:
from scapy.all import *
import random
sp=random.randint(1024,65535)
ip=IP(src="10.0.0.234/29",dst="www.google.com")
SYN=TCP(sport=sp, dport=80,flags="S",seq=10)
SYNACK=sr1(ip/SYN)
my_ack=SYNACK.seq+1
ACK=TCP(sport=sp,dport=80,flags="A",seq=11,ack=my_ack)
send(ip/ACK)
payload="SEND TCP"
PUSH=TCP(sport=sp,dport=80,flags="PA",seq=11,ack=my_ack)
send(ip/PUSH/payload)
Because you are behind a NAT/router, you should check it allows you to use the full range of IPs. If it is running DHCP protocol, your eth0 will typically recieve a unique IP adress that will be the only routed in your private network.
Furthermore, you must ensure your kernel knows what IPs are attributed to it, else it will drop response packets. If you want to use the full range of IP, you have two choices :
Create virtual devices with virtual mac adresses, each requesting an IP through DHCP.
Configure your router so it statically routes the full IP table to your host, and alias each IP you intend to use
Once you have done that, there is no reason you wouldn't be able to syn/ack from your multiple source IPs. From distant server point of view, there wouldn't be any difference between what you are trying to do and several machines in a local network requesting a page at the same time.