ping_remote_host.py

#!/usr/bin/env python


import os
import argparse
import socket
import struct
import select
import time

ICMP_ECHO_REQUEST = 8  # platform specific
DEFAULT_TIMEOUT = 2
DEFAULT_COUNT = 4


class Pinger(object):
    """ Ping a host the Python way"""
    def __init__(self, target_host, count=DEFAULT_COUNT, timeout=DEFAULT_TIMEOUT):
        self.target_host = target_host
        self.count = count
        self.timeout = timeout

    def do_checksum(self, source_string):
        """ Verify packet integrity """
        sum = 0
        max_count = (len(source_string)/2) *2
        count = 0
        while count < max_count:
            val = ord(source_string[count + 1])*256 + ord(source_string[count])
            sum = sum + val
            sum = sum & 0xffffffff
            count = count + 2
        if max_count<len(source_string):
            sum = sum + ord(source_string[len(source_string) - 1])
            sum = sum & 0xffffffff
        sum = (sum >> 16) + (sum & 0xffff)
        sum = sum + (sum >> 16)
        answer = ~sum
        answer = answer & 0xffff
        answer = answer >> 8 | (answer << 8 & 0xff00)
        return answer

    def receive_pong(self, sock, ID, timeout):
        """ Receive ping from socket """
        time_remaining = timeout
        while True:
            start_time = time.time()
            readable = select.select([sock], [], [], time_remaining)
            time_spent = (time.time() - start_time)
            if readable[0] == []:  # timeout
                return

            time_received = time.time()
            recv_packet, addr = sock.recvfrom(1024)
            icmp_header = recv_packet[20:28]
            type, code, checksum, packet_ID, sequence = struct.unpack(
                "bbHHh", icmp_header
                )
            if packet_ID == ID:
                bytes_In_double = struct.calcsize("d")
                time_sent = struct.unpack("d", recv_packet[28:28 + bytes_In_double]) [0]
                return time_received - time_sent
                time_remaining = time_remaining - time_spent
                if time_remaining <= 0:
                    return

    def send_ping(self, sock, ID):
        """ Ping the target """
        target_addr = socket.gethostbyname(self.target_host)
        my_checksum = 0
        # create a dummy header with a 0 checksum.
        header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, my_checksum, ID, 1)
        bytes_In_double = struct.calcsize("d")
        data = (192 - bytes_In_double) * "Q"
        data = struct.pack("d", time.time()) + data
        # get the checksum on the data and the dummy header.
        my_checksum = self.do_checksum(header + data)
        header = struct.pack(
            "bbHHh", ICMP_ECHO_REQUEST, 0, socket.htons(my_checksum), ID, 1
            )
        packet = header + data
        sock.sendto(packet, (target_addr, 1))

    def ping_once(self):
        """ returns delay in seconds or none on timeout. """
        icmp = socket.getprotobyname("icmp")
        try:
            sock = socket.socket(socket.AF_INET, socket.SOCK_RAW, icmp)
        except socket.error, (errno, msg):
            if errno == 1:
                # need root privs
                msg += " need root privs to send icmp"
                raise socket.error(msg)
        except Exception, e:
            print "Exception: %s" %(e)
            my_ID = os.getpid() & 0xFFFF
            self.send_ping(sock, my_ID)
            delay = self.receive_pong(sock, my_ID, self.timeout)
            sock.close()
            return delay

    def ping(self):
        """ run ping """
        for i in xrange(self.count):
            print "Ping to %s..." % self.target_host,
            try:
                delay = self.ping_once()
            except socket.gaierror, e:
                print "Ping failed. (socket error: '%s')" % e[1]
                break
            if delay == None:
                print "Ping failed. (timeout within %ssec.)" % \
                            self.timeout
            else:
                delay = delay * 1000
                print "Get pong in %0.4fms" % delay

if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Python ping')
    parser.add_argument('--target-host', action="store", dest="target_host", required=True)
    given_args = parser.parse_args()
    target_host = given_args.target_host
    pinger = Pinger(target_host=target_host)
    pinger.ping()