Re: How to ping in Python?

Nico Grubert wrote: 
Hi there,

I could not find any "ping" Class or Handler in python (2.3.5) to ping a machine.
I just need to "ping" a machine to see if its answering. What's the best way to do it?

Kind regards,
Nico



# Derived from ping.c distributed in Linux's netkit. That code is
# copyright (c) 1989 by The Regents of the University of California.
# That code is in turn derived from code written by Mike Muuss of the
# US Army Ballistic Research Laboratory in December, 1983 and
# placed in the public domain. They have my thanks.

# Bugs are naturally mine. I'd be glad to hear about them. There are
# certainly word-size dependenceies here.

# Copyright (c) Matthew Dixon Cowles, <http://www.visi.com/~mdc/>.
# Distributable under the terms of the GNU General Public License
# version 2. Provided with no warranties of any sort.

# Note that ICMP messages can only be sent from processes running
# as root.

# Revision history:
#
# November 22, 1997
# Initial hack. Doesn't do much, but rather than try to guess
# what features I (or others) will want in the future, I've only
# put in what I need now.
#
# December 16, 1997
# For some reason, the checksum bytes are in the wrong order when
# this is run under Solaris 2.X for SPARC but it works right under
# Linux x86. Since I don't know just what's wrong, I'll swap the
# bytes always and then do an htons().
#
# December 4, 2000
# Changed the struct.pack() calls to pack the checksum and ID as
# unsigned. My thanks to Jerome Poincheval for the fix.
#

# From /usr/include/linux/icmp.h; your milage may vary.
ICMP_ECHO_REQUEST = 8 # Seems to be the same on Solaris.

# I'm not too confident that this is right but testing seems
# to suggest that it gives the same answers as in_cksum in ping.c
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 # Necessary?
        count = count + 2

    if countTo < len(str):
        csum = csum + ord(str[len(str) - 1])
        csum = csum & 0xffffffffL # Necessary?

    csum = (csum >> 16) + (csum & 0xffff)
    csum = csum + (csum >> 16)
    answer = ~csum
    answer = answer & 0xffff

    # Swap bytes. Bugger me if I know why.
    answer = answer >> 8 | (answer << 8 & 0xff00)

    return answer

def receiveOnePing(mySocket, ID, timeout):
    timeLeft = timeout

    while 1:
        startedSelect = time.time()
        whatReady = select.select([mySocket], [], [], timeLeft)
        howLongInSelect = (time.time() - startedSelect)

        if whatReady[0] == []: # Timeout
            return -1

timeReceived = time.time()
recPacket, addr = mySocket.recvfrom(1024)
icmpHeader = recPacket[20:28]
typ, code, checksum, packetID, sequence = struct.unpack("bbHHh", icmpHeader)

if packetID == ID:
bytesInDouble = struct.calcsize("d")
timeSent = struct.unpack("d", recPacket[28:28 + bytesInDouble])[0]
return timeReceived - timeSent

        timeLeft = timeLeft - howLongInSelect

        if timeLeft <= 0:
            return -1

def sendOnePing(mySocket, destAddr, ID):
    # Header is type (8), code (8), checksum (16), id (16), sequence (16)
    myChecksum = 0

    # Make a dummy heder with a 0 checksum.
    header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, myChecksum, ID, 1)
    bytesInDouble = struct.calcsize("d")
    data = (192 - bytesInDouble) * "Q"
    data = struct.pack("d", time.time()) + data

    # Calculate the checksum on the data and the dummy header.
    myChecksum = checksum(header + data)

    # Now that we have the right checksum, we put that in. It's just easier
    # to make up a new header than to stuff it into the dummy.
    if prop.platform == 'darwin':
        myChecksum = socket.htons(myChecksum) & 0xffff
    else:
        myChecksum = socket.htons(myChecksum)

    header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0,
                        myChecksum, ID, 1)

    packet = header + data
    mySocket.sendto(packet, (destAddr, 1)) # Don't know about the 1

def doOne(destAddr, timeout=10):
    # Returns either the delay (in seconds) or none on timeout.
    icmp = socket.getprotobyname("icmp")
    mySocket = socket.socket(socket.AF_INET,socket.SOCK_RAW,icmp)
    myID = os.getpid() & 0xFFFF
    sendOnePing(mySocket, destAddr, myID)
    delay = receiveOnePing(mySocket, myID, timeout)
    mySocket.close()

    return delay


def ping(host, timeout=1):
    dest = socket.gethostbyname(host)
    delay = doOne(dest, timeout)
    return delay

.

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