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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