How to ping in Python?

[Nico Grubert]

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

[dudeman]

Try the PyNMS libraries:
http://freshmeat.net/projects/pynms/

It has a ping module. If all you need is the ping module, maybe you
could just look through that code and see if it's relatively simple to
impliment yourself.

[dwelch]

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_REQUE ST = 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.recvfr om(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(myS ocket, 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("bb HHh", ICMP_ECHO_REQUE ST, 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(my Checksum) & 0xffff
else:
myChecksum = socket.htons(my Checksum)

header = struct.pack("bb HHh", ICMP_ECHO_REQUE ST, 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.getproto byname("icmp")
mySocket = socket.socket(s ocket.AF_INET,s ocket.SOCK_RAW, icmp)
myID = os.getpid() & 0xFFFF
sendOnePing(myS ocket, destAddr, myID)
delay = receiveOnePing( mySocket, myID, timeout)
mySocket.close( )

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

[Larry Bates]

Seems that you must change the following lines to work:

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

to

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

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_REQUE ST = 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.recvfr om(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(myS ocket, 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("bb HHh", ICMP_ECHO_REQUE ST, 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(my Checksum) & 0xffff
else:
myChecksum = socket.htons(my Checksum)

header = struct.pack("bb HHh", ICMP_ECHO_REQUE ST, 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.getproto byname("icmp")
mySocket = socket.socket(s ocket.AF_INET,s ocket.SOCK_RAW, icmp)
myID = os.getpid() & 0xFFFF
sendOnePing(myS ocket, destAddr, myID)
delay = receiveOnePing( mySocket, myID, timeout)
mySocket.close( )

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

[Michael Schneider]

I telnet to port 13 (returns time)

Hope this is helpful,
Mike

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

--
The greatest performance improvement occurs on the transition of from
the non-working state to the working state.

[Michael Schneider]

I telnet to port 13 (returns time)

Hope this is helpful,
Mike

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

--
The greatest performance improvement occurs on the transition of from
the non-working state to the working state.

[Laszlo Zsolt Nagy]

Michael Schneider wrote:

I telnet to port 13 (returns time)

The problem is that most modern up-to-date servers use firewalls. They
only open the ports that are absolutely necessary. Usually the time
service is part of inetd, which is disabled by default, on most of the
servers. PING ICMP may work, but sometimes it does not either. In the
worst case, all port are closed and you have no way to tell if there is
a computer or not.

Can you tell more about what kind of server do you need to "ping"?

Example: if you need to know if a web server is alive, you should
connect to port 80 (http). If the connection was successful, you can
close the connection immeditelly. You can expect a HTTP server to open
the HTTP port, but all other ports may be closed.

Les

[Michael Schneider]

Les,

I only ping internal machines. You are right about shutting down ports.

When we disable telent, we also disable ping. Many people may not though,

good luck,
Mike

Laszlo Zsolt Nagy wrote:

Michael Schneider wrote:

I telnet to port 13 (returns time)

The problem is that most modern up-to-date servers use firewalls. They
only open the ports that are absolutely necessary. Usually the time
service is part of inetd, which is disabled by default, on most of the
servers. PING ICMP may work, but sometimes it does not either. In the
worst case, all port are closed and you have no way to tell if there
is a computer or not.

Can you tell more about what kind of server do you need to "ping"?

Example: if you need to know if a web server is alive, you should
connect to port 80 (http). If the connection was successful, you can
close the connection immeditelly. You can expect a HTTP server to open
the HTTP port, but all other ports may be closed.

Les

--
The greatest performance improvement occurs on the transition of from the non-working state to the working state.

[Sybren Stuvel]

Nico Grubert enlightened us with:

I just need to "ping" a machine to see if its answering. What's the
best way to do it?

To do a real ICMP ping, you need raw sockets, which are turned off on
Windows and reserved for root on other systems. You could try to
connect to an unused port, and see how fast a RST packet is returned.

Sybren
--
The problem with the world is stupidity. Not saying there should be a
capital punishment for stupidity, but why don't we just take the
safety labels off of everything and let the problem solve itself?
Frank Zappa