I’ve been looking for a pure python implementation of the ping command. Now that I found one, I am not sure if I want to use it, as it has a restriction: only privileged users can ping other hosts. I’ve used the ping command successfully as a normal user on all operating systems I have tried and never had an issue. Currently, I do not have the time to investigate this limitation, but, judging by the exception I get, it has to do with the creation of the socket through which the ICMP packet is sent. The normal user does not have the required privileges to create this socket.
[This post has been updated]
[Update #1]: This limitation also exists on the ping command, which runs with setuid access rights. (Thanks Stephane)
[Update #2]: After Chris Hallman reported that the original code actually works on Windows only, I made some changes to it and publish the updated code below.
The following code is a pure Python implementation of the ping command. I originally found it in the source code tree of pylucid in a subdirectory where the developers keep various code snippets.
I had originally tested the code under Microsoft Windows as this was the OS I had available at the moment. Chris Hallman noticed that the code does not work under GNU/Linux. After spending some hours trying to figure out what was wrong it, I realized that the part of the code that caused the failure on Linux was the use of the
time.clock() function instead of
clock() method works differently under Windows and Linux.
I fixed the 2007 implementation and hereby publish the updated code(as python-ping). Feel free to test it and report any issues.
Needed: test on Solaris.
#!/usr/bin/env python """ A pure python ping implementation using raw socket. Note that ICMP messages can only be sent from processes running as root. 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. Original Version from Matthew Dixon Cowles: -> ftp://ftp.visi.com/users/mdc/ping.py Rewrite by Jens Diemer: -> http://www.python-forum.de/post-69122.html#69122 Rewrite by George Notaras: -> http://www.g-loaded.eu/2009/10/30/python-ping/ Revision history ~~~~~~~~~~~~~~~~ November 8, 2009 ---------------- Improved compatibility with GNU/Linux systems. Fixes by: * George Notaras -- http://www.g-loaded.eu Reported by: * Chris Hallman -- http://cdhallman.blogspot.com Changes in this release: - Re-use time.time() instead of time.clock(). The 2007 implementation worked only under Microsoft Windows. Failed on GNU/Linux. time.clock() behaves differently under the two OSes.  http://docs.python.org/library/time.html#time.clock May 30, 2007 ------------ little rewrite by Jens Diemer: - change socket asterisk import to a normal import - replace time.time() with time.clock() - delete "return None" (or change to "return" only) - in checksum() rename "str" to "source_string" 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. Last commit info: ~~~~~~~~~~~~~~~~~ $LastChangedDate: $ $Rev: $ $Author: $ """ import os, sys, socket, struct, select, time # From /usr/include/linux/icmp.h; your milage may vary. ICMP_ECHO_REQUEST = 8 # Seems to be the same on Solaris. def checksum(source_string): """ 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 """ sum = 0 countTo = (len(source_string)/2)*2 count = 0 while count<countTo: thisVal = ord(source_string[count + 1])*256 + ord(source_string[count]) sum = sum + thisVal sum = sum & 0xffffffff # Necessary? count = count + 2 if countTo<len(source_string): sum = sum + ord(source_string[len(source_string) - 1]) sum = sum & 0xffffffff # Necessary? sum = (sum >> 16) + (sum & 0xffff) sum = sum + (sum >> 16) answer = ~sum answer = answer & 0xffff # Swap bytes. Bugger me if I know why. answer = answer >> 8 | (answer << 8 & 0xff00) return answer def receive_one_ping(my_socket, ID, timeout): """ receive the ping from the socket. """ timeLeft = timeout while True: startedSelect = time.time() whatReady = select.select([my_socket], , , timeLeft) howLongInSelect = (time.time() - startedSelect) if whatReady == : # Timeout return timeReceived = time.time() recPacket, addr = my_socket.recvfrom(1024) icmpHeader = recPacket[20:28] type, code, checksum, packetID, sequence = struct.unpack( "bbHHh", icmpHeader ) if packetID == ID: bytesInDouble = struct.calcsize("d") timeSent = struct.unpack("d", recPacket[28:28 + bytesInDouble]) return timeReceived - timeSent timeLeft = timeLeft - howLongInSelect if timeLeft <= 0: return def send_one_ping(my_socket, dest_addr, ID): """ Send one ping to the given >dest_addr<. """ dest_addr = socket.gethostbyname(dest_addr) # Header is type (8), code (8), checksum (16), id (16), sequence (16) my_checksum = 0 # Make a dummy heder with a 0 checksum. header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, my_checksum, 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. my_checksum = 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. header = struct.pack( "bbHHh", ICMP_ECHO_REQUEST, 0, socket.htons(my_checksum), ID, 1 ) packet = header + data my_socket.sendto(packet, (dest_addr, 1)) # Don't know about the 1 def do_one(dest_addr, timeout): """ Returns either the delay (in seconds) or none on timeout. """ icmp = socket.getprotobyname("icmp") try: my_socket = socket.socket(socket.AF_INET, socket.SOCK_RAW, icmp) except socket.error, (errno, msg): if errno == 1: # Operation not permitted msg = msg + ( " - Note that ICMP messages can only be sent from processes" " running as root." ) raise socket.error(msg) raise # raise the original error my_ID = os.getpid() & 0xFFFF send_one_ping(my_socket, dest_addr, my_ID) delay = receive_one_ping(my_socket, my_ID, timeout) my_socket.close() return delay def verbose_ping(dest_addr, timeout = 2, count = 4): """ Send >count< ping to >dest_addr< with the given >timeout< and display the result. """ for i in xrange(count): print "ping %s..." % dest_addr, try: delay = do_one(dest_addr, timeout) except socket.gaierror, e: print "failed. (socket error: '%s')" % e break if delay == None: print "failed. (timeout within %ssec.)" % timeout else: delay = delay * 1000 print "get ping in %0.4fms" % delay print if __name__ == '__main__': verbose_ping("heise.de") verbose_ping("google.com") verbose_ping("a-test-url-taht-is-not-available.com") verbose_ping("192.168.1.1")
ping.py – Python Implementation of the ping command by George Notaras is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
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