Finding local IP addresses using Python's stdl-第2页回答

2楼-- · 2018-12-31 06:24

Socket API method

see https://stackoverflow.com/a/28950776/711085

Downsides:

Not cross-platform.
Requires more fallback code, tied to existence of particular addresses on the internet
This will also not work if you're behind a NAT
Probably creates a UDP connection, not independent of (usually ISP's) DNS availability (see other answers for ideas like using 8.8.8.8: Google's (coincidentally also DNS) server)
Make sure you make the destination address UNREACHABLE, like a numeric IP address that is spec-guaranteed to be unused. Do NOT use some domain like fakesubdomain.google.com or somefakewebsite.com; you'll still be spamming that party (now or in the future), and spamming your own network boxes as well in the process.

Reflector method

(Do note that this does not answer the OP's question of the local IP address, e.g. 192.168...; it gives you your public IP address, which might be more desirable depending on use case.)

You can query some site like whatismyip.com (but with an API), such as:

from urllib.request import urlopen
import re
def getPublicIp():
    data = str(urlopen('http://checkip.dyndns.com/').read())
    # data = '<html><head><title>Current IP Check</title></head><body>Current IP Address: 65.96.168.198</body></html>\r\n'

    return re.compile(r'Address: (\d+\.\d+\.\d+\.\d+)').search(data).group(1)

or if using python2:

from urllib import urlopen
import re
def getPublicIp():
    data = str(urlopen('http://checkip.dyndns.com/').read())
    # data = '<html><head><title>Current IP Check</title></head><body>Current IP Address: 65.96.168.198</body></html>\r\n'

    return re.compile(r'Address: (\d+\.\d+\.\d+\.\d+)').search(data).group(1)

Advantages:

One upside of this method is it's cross-platform
It works from behind ugly NATs (e.g. your home router).

Disadvantages (and workarounds):

Requires this website to be up, the format to not change (almost certainly won't), and your DNS servers to be working. One can mitigate this issue by also querying other third-party IP address reflectors in case of failure.
Possible attack vector if you don't query multiple reflectors (to prevent a compromised reflector from telling you that your address is something it's not), or if you don't use HTTPS (to prevent a man-in-the-middle attack pretending to be the server)

edit: Though initially I thought these methods were really bad (unless you use many fallbacks, the code may be irrelevant many years from now), it does pose the question "what is the internet?". A computer may have many interfaces pointing to many different networks. For a more thorough description of the topic, google for gateways and routes. A computer may be able to access an internal network via an internal gateway, or access the world-wide web via a gateway on for example a router (usually the case). The local IP address that the OP asks about is only well-defined with respect to a single link layer, so you have to specify that ("is it the network card, or the ethernet cable, which we're talking about?"). There may be multiple non-unique answers to this question as posed. However the global IP address on the world-wide web is probably well-defined (in the absence of massive network fragmentation): probably the return path via the gateway which can access the TLDs.

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姐姐魅力值爆表

3楼-- · 2018-12-31 06:24

127.0.1.1 is your real IP address. More generally speaking, a computer can have any number of IP addresses. You can filter them for private networks - 127.0.0.0/8, 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16.

However, there is no cross-platform way to get all IP addresses. On Linux, you can use the SIOCGIFCONF ioctl.

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皆成旧梦

4楼-- · 2018-12-31 06:27

This method returns the "primary" IP on the local box (the one with a default route).

Does NOT need routable net access or any connection at all.
Works even if all interfaces are unplugged from the network.
Does NOT need or even try to get anywhere else.
Works with NAT, public, private, external, and internal IP's
Pure Python 2 (or 3) with no external dependencies.
Works on Linux, Windows, and OSX.

Python 2 or 3:

import socket
def get_ip():
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    try:
        # doesn't even have to be reachable
        s.connect(('10.255.255.255', 1))
        IP = s.getsockname()[0]
    except:
        IP = '127.0.0.1'
    finally:
        s.close()
    return IP

This returns a single IP which is the primary (the one with a default route). If you need instead all IP's attached to all interfaces (including localhost, etc), see this answer.

If you are behind a NAT firewall like your wifi box at home, then this will not show your public NAT IP, but instead your private NAT IP on the local network which has a default route to your local WIFI router; getting your wifi router's external IP would either require running this on THAT box, or connecting to an external service such as whatismyip.com/whatismyipaddress.com that could reflect back the IP... but that is completely different from the original question. :)

Updated connect() call per Pedro's suggestion in comments. (If you need a specific license statement, this is public domain/free for any use, or MIT/CC2-BY-SA per Stack Overflow's code/content license at your option.)

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人间绝色

5楼-- · 2018-12-31 06:27

FYI I can verify that the method:

import socket
addr = socket.gethostbyname(socket.gethostname())

Works in OS X (10.6,10.5), Windows XP, and on a well administered RHEL department server. It did not work on a very minimal CentOS VM that I just do some kernel hacking on. So for that instance you can just check for a 127.0.0.1 address and in that case do the following:

if addr == "127.0.0.1":
     import commands
     output = commands.getoutput("/sbin/ifconfig")
     addr = parseaddress(output)

And then parse the ip address from the output. It should be noted that ifconfig is not in a normal user's PATH by default and that is why I give the full path in the command. I hope this helps.

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不流泪的眼

6楼-- · 2018-12-31 06:29

I'm afraid there aren't any good platform independent ways to do this other than connecting to another computer and having it send you your IP address. For example: findmyipaddress. Note that this won't work if you need an IP address that's behind NAT unless the computer you're connecting to is behind NAT as well.

Here's one solution that works in Linux: get the IP address associated with a network interface.

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墨雨无痕

7楼-- · 2018-12-31 06:29

One simple way to produce "clean" output via command line utils:

import commands
ips = commands.getoutput("/sbin/ifconfig | grep -i \"inet\" | grep -iv \"inet6\" | " +
                         "awk {'print $2'} | sed -ne 's/addr\:/ /p'")
print ips

It will show all IPv4 addresses on the system.

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Finding local IP addresses using Python's stdl

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