python: check wether a hostname/IP refers to the localhost

host_is_local.py

"""
check if an ip address or hostname is local.
NOTE: IPv6 support is NOT 100% tested. Some IPv6 addresses seem to work, others not.
"""
import socket


def host_is_local(hostname, port=None):
    """returns True if the hostname points to the localhost, otherwise False."""
    if port is None:
        port = 22  # no port specified, lets just use the ssh port
    hostname = socket.getfqdn(hostname)
    if hostname in ("localhost", "0.0.0.0"):
        return True
    localhost = socket.gethostname()
    localaddrs = socket.getaddrinfo(localhost, port)
    targetaddrs = socket.getaddrinfo(hostname, port)
    for (family, socktype, proto, canonname, sockaddr) in localaddrs:
        for (rfamily, rsocktype, rproto, rcanonname, rsockaddr) in targetaddrs:
            if rsockaddr[0] == sockaddr[0]:
                return True
    return False

if __name__ == "__main__":
    i = raw_input("Please enter an hostname or IP: ")
    il = host_is_local(i)
    if il:
        print "Hostname/IP is the localhost."
    else:
        print "Hostname/IP is not the localhost."