How to ping in Python?

[Larry Bates]

Seems that you must change the following lines to work:

    if prop.platform == 'darwin':
        myChecksum = socket.htons(myChecksum) & 0xffff
    else:
        myChecksum = socket.htons(myChecksum)

to

    if sys.platform == 'darwin':
        myChecksum = socket.htons(myChecksum) & 0xffff
    else:
        myChecksum = socket.htons(myChecksum)

You also must import the following modules:

import socket
import os
import sys
import struct
import time
import select

-Larry Bates

dwelch wrote:
> 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
>