ping example

ping_client.py

#!/usr/bin/env python
#-*- coding:utf-8 -*-

import socket
import time
import struct
import datetime

def calculate_checksum(s):
    csum = reduce(lambda a,b: a+b,
                  [struct.unpack("!h",s[i*2:(i+1)*2])[0] for i in range(len(s)/2)])
    csum = (0xffff & csum) + (csum >> 16)
    return 0xffff & ~csum

def ping(ip_addr, icmp_seq):
    # create a socket
    sock = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_ICMP)

    # compose icmp payload
    icmp_s_type = 8 # Echo Request
    icmp_s_code = 0
    icmp_s_id = 1
    icmp_s_seq = icmp_seq
    icmp_s_data = b"abcdefghijklmnopqrstuvwxyz"

    icmp_s_payload = struct.pack("!2B2H", icmp_s_type, icmp_s_code, icmp_s_id, icmp_s_seq)
    icmp_s_payload += icmp_s_data

    # calculate checksum

    csum = calculate_checksum(icmp_s_payload)
    #print "CheckSum:", hex(csum)

    icmp_s_payload = icmp_s_payload[:4] + struct.pack("!h", csum) + icmp_s_payload[4:]

    # send the icmp packet
    start_time = datetime.datetime.now()
    sock.sendto(icmp_s_payload, ip_addr)

    # receive the packet
    data = sock.recv(255)[20:]
    end_time = datetime.datetime.now()

    delta = end_time - start_time

    # decompose packet
    icmp_r_type, icmp_r_code, icmp_r_checksum, icmp_r_id, icmp_r_seq, icmp_r_data = \
        struct.unpack("!2B3H%ds" % (len(data)-8), data)

    # check the result
    try:
        assert(icmp_r_type == 0)
        assert(icmp_r_code == 0)
        assert(icmp_r_seq == icmp_s_seq)
        assert(icmp_r_data == icmp_s_data)
        assert(icmp_r_checksum == calculate_checksum(data[:2]+data[4:]))
    except AssertionError as e:
        print e.args
        raise

    return len(data), delta.total_seconds() * 1000.0

def main():
    ip_addr = ("localhost",0)
    for i in range (100):
        size, delta = ping(ip_addr, i)
        print "%s bytes from %s: icmp_seq=%d time=%0.3f ms" % (size, ip_addr[0], i, delta)
        time.sleep(1)


if __name__ == "__main__":
    main()