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Socket Programming Assignment 5: ICMP Pinger
import os
import sys
import struct
import time
import select
import socket
import binascii
ICMP_ECHO_REQUEST = 8
def checksum(str):
csum = 0
countTo = (len(str) / 2) * 2
count = 0
while count < countTo:
thisVal = ord(str[count+1]) * 256 + ord(str[count])
csum = csum + thisVal
csum = csum & 0xffffffffL
count = count + 2
if countTo < len(str):
csum = csum + ord(str[len(str) - 1])
csum = csum & 0xffffffffL
csum = (csum >> 16) + (csum & 0xffff)
csum = csum + (csum >> 16)
answer = ~csum
answer = answer & 0xffff
answer = answer >> 8 | (answer << 8 & 0xff00)
return answer
def receiveOnePing(mySocket, ID, timeout, destAddr):
global rtt_min, rtt_max, rtt_sum, rtt_cnt
timeLeft = timeout
while 1:
startedSelect = time.time()
whatReady = select.select([mySocket], [], [], timeLeft)
howLongInSelect = (time.time() - startedSelect)
if whatReady[0] == []: # Timeout
return "Request timed out."
timeReceived = time.time()
recPacket, addr = mySocket.recvfrom(1024)
#Fill in start
#Fetch the ICMP header from the IP packet
type, code, checksum, id, seq = struct.unpack('bbHHh', recPacket[20:28])
if type != 0:
return 'expected type=0, but got {}'.format(type)
if code != 0:
return 'expected code=0, but got {}'.format(code)
if ID != id:
return 'expected id={}, but got {}'.format(ID, id)
send_time, = struct.unpack('d', recPacket[28:])
rtt = (timeReceived - send_time) * 1000
rtt_cnt += 1
rtt_sum += rtt
rtt_min = min(rtt_min, rtt)
rtt_max = max(rtt_max, rtt)
ip_header = struct.unpack('!BBHHHBBH4s4s' , recPacket[:20])
ttl = ip_header[5]
saddr = socket.inet_ntoa(ip_header[8])
length = len(recPacket) - 20
return '{} bytes from {}: icmp_seq={} ttl={} time={:.3f} ms'.format(length, saddr, seq, ttl, rtt)
#Fill in end
timeLeft = timeLeft - howLongInSelect
if timeLeft <= 0:
return "Request timed out."
def sendOnePing(mySocket, destAddr, ID):
# Header is type (8), code (8), checksum (16), id (16), sequence (16)
myChecksum = 0
# Make a dummy header with a 0 checksum.
# struct -- Interpret strings as packed binary data
header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, myChecksum, ID, 1)
data = struct.pack("d", time.time())
# Calculate the checksum on the data and the dummy header.
myChecksum = checksum(header + data)
# Get the right checksum, and put in the header
if sys.platform == 'darwin':
myChecksum = socket.htons(myChecksum) & 0xffff
#Convert 16-bit integers from host to network byte order.
else:
myChecksum = socket.htons(myChecksum)
header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, myChecksum, ID, 1)
packet = header + data
mySocket.sendto(packet, (destAddr, 1)) # AF_INET address must be tuple, not str
#Both LISTS and TUPLES consist of a number of objects
#which can be referenced by their position number within the object
def doOnePing(destAddr, timeout):
icmp = socket.getprotobyname("icmp")
#SOCK_RAW is a powerful socket type. For more details see: http://sock-raw.org/papers/sock_raw
#Fill in start
#Create Socket here
mySocket = socket.socket(socket.AF_INET, socket.SOCK_RAW, icmp)
#Fill in end
myID = os.getpid() & 0xFFFF #Return the current process i
sendOnePing(mySocket, destAddr, myID)
delay = receiveOnePing(mySocket, myID, timeout, destAddr)
mySocket.close()
return delay
def ping(host, timeout=1):
global rtt_min, rtt_max, rtt_sum, rtt_cnt
rtt_min = float('+inf')
rtt_max = float('-inf')
rtt_sum = 0
rtt_cnt = 0
cnt = 0
#timeout=1 means: If one second goes by without a reply from the server,
#the client assumes that either the client's ping or the server's pong is lost
dest = socket.gethostbyname(host)
print "Pinging " + dest + " using Python:"
#Send ping requests to a server separated by approximately one second
try:
while True:
cnt += 1
print doOnePing(dest, timeout)
time.sleep(1)
except KeyboardInterrupt:
if cnt != 0:
print '--- {} ping statistics ---'.format(host)
print '{} packets transmitted, {} packets received, {:.1f}% packet loss'.format(cnt, rtt_cnt, 100.0 - rtt_cnt * 100.0 / cnt)
if rtt_cnt != 0:
print 'round-trip min/avg/max {:.3f}/{:.3f}/{:.3f} ms'.format(rtt_min, rtt_sum / rtt_cnt, rtt_max)
ping(sys.argv[1])
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