print ("Measure the hop distance and RTT of " + desthost)

destaddr = socket.gethostbyname(desthost) #get the ip address for a given hsot

#print (destaddr)

port = 33435 #port used in the destination port field in udp packet

udp = socket.getprotobyname("udp")

icmp = socket.getprotobyname("icmp")

ttl = 32 #the initial TTL in the ip header will be this

#use UDP segment to test a host, the UDP segment is send to a port that is unlikely to be used in destination host

#create a sending socket using udp protocol

sendsocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, udp)

sendsocket.setsockopt(socket.SOL_IP, socket.IP_TTL, ttl) #set the ttl field in IP header

#create a receiving socket as a raw socket, using icmp protocol, in order to receive all the IP datagram

recvsocket = socket.socket(socket.AF_INET, socket.SOCK_RAW, icmp)

sendtime = send(destaddr, sendsocket, port)

TTL, arrivedtime = getreply(recvsocket, destaddr, port)

if TTL:

delay = arrivedtime - sendtime

delay = 1000*delay #delay is going to be showed in the unit of ms.

TTL = 32 - TTL #subtracting 32 with the remaining TTL in the header field to get the hop distance

print ("Destination host: %s, Hop distance: %s, RTT: %1.1fms" %(desthost, TTL, delay))

sendsocket.close()

#send the artificial to a port that is unlikely to be used on the remote host

try:

a = sendsocket.sendto(struct.pack("d", time.time()), (destaddr,port))

#print (a)

except socket.error, e:

print ("failed. (socket error: '%s')" % e[1])

return

sendtime = time.time()

#recording the send time and return it for calculating RTT

#print (sendtime)

#use the raw socket to receive the icmp packet in order to parse it.

#timeout = 10s

start = time.time()

timeout = 10.0

who = None

packet = None

myname = socket.getfqdn(socket.gethostname())

myaddr = socket.gethostbyname(myname) #get the ip address for my own computer

#print ("start to listen")

while 1:

rd, wt, er = select.select([recvsocket], [], [], timeout)

if rd:

try:

packet, who = recvsocket.recvfrom(4096)

except Exception:

pass

#print (who)

#(daddr, dport) = who

#print (daddr)

#print (packet)

arrivedtime = time.time()

#record the arriving time of ICMP packet and return it for calculating RTT

#parsing thr receiving IP datagram

icmpheader = packet[20:24]

#print (icmpheader)

icmpdata = packet[28:]

type, code, checksum = struct.unpack("bbH", icmpheader)

print ("received ICMP packet of " + "type: %d code: %d" %(type, code))

origipheader = icmpdata[ :20]

(TTL, )= struct.unpack("b", origipheader[8])

#print (TTL)

saddr = origipheader[12:16]

(saddr, ) = struct.unpack("4s", saddr)

saddr = socket.inet_ntoa(saddr)

#print (saddr)

daddr = origipheader[16:20]

(daddr, ) = struct.unpack("4s", daddr)

daddr = socket.inet_ntoa(daddr)

#print (daddr)

udpheader = icmpdata[20:28]

# sport = struct.unpack("H", udpheader[ :2])

# print (sport)

# dport = struct.unpack("H", udpheader[2:4])

# print (dport)

#the source port and destination port seems to be changed from the original value, cannot use them to match the packet.

#if the packet belongs to our distMeasutrement tool

if daddr == destaddr:

#if saddr == myaddr:

#cannot use source address to match the packet if the computer is used within a NAT network

#since the source address will be changed when passing the NAT-enabled router

if type == 3:

if code == 3:

return TTL, arrivedtime

timeout = (start + timeout) - time.time()

if timeout < 0:

print ("failed! timeout within 10.0 seconds")

#reading txt file

f = open("targets.txt", "r")

targets = f.readlines()

#print targets

for target in targets:

target = target.split("\n")[0]

print target