Provided by: 2ping_1.2.3-1_all bug


       2ping - A bi-directional ping client/listener


       2ping [ options ] --listen | host/IP


       2ping is a bi-directional ping utility.  It uses 3-way pings (akin to TCP SYN, SYN/ACK,
       ACK) and after-the-fact state comparison between a 2ping listener and a 2ping client to
       determine which direction packet loss occurs.

       To use 2ping, start a listener on a known stable network host.  The relative network
       stability of the 2ping listener host should not be in question, because while 2ping can
       determine whether packet loss is occurring inbound or outbound relative to an endpoint,
       that will not help you determine the cause if both of the endpoints are in question.

       Once the listener is started, start 2ping in client mode and tell it to connect to the
       listener.  The ends will begin pinging each other and displaying network statistics.  If
       packet loss occurs, 2ping will wait a few seconds (default 10, configurable with -w)
       before comparing notes between the two endpoints to determine which direction the packet
       loss is occurring.

       To quit 2ping on the client or listener ends, enter ^C, and a list of statistics will be
       displayed.  To get a short inline display of statistics without quitting, send the process
       a QUIT signal (yes, that's the opposite of what you would think, but it's in line with the
       normal ping utility).


       ping-compatible options:

       -a  Audible ping.

       -A  Adaptive ping.  A new client ping request is sent as soon as a client ping response is
           received.  If a ping response is not received within the interval period, a new ping
           request is sent.  Minimal interval is 200msec for not super-user.  On networks with
           low rtt this mode is essentially equivalent to flood mode.

           2ping-specific notes: This behavior is somewhat different to the nature of ping's
           adaptive ping, but the result is roughly the same.

       -c count
           Stop after sending count ping requests.

           2ping-specific notes: This option behaves slightly differently from ping.  If both -c
           and -w are specified, satisfaction of -c will cause an exit first.  Also, internally,
           2ping exits just before sending count+1 pings, to give time for the ping to complete.

       -f  Flood ping. For every ping sent a period "." is printed, while for ever ping received
           a backspace is printed. This provides a rapid display of how many pings are being
           dropped.  If interval is not given, it sets interval to zero and outputs pings as fast
           as they come back or one hundred times per second, whichever is more.  Only the super-
           user may use this option with zero interval.

           2ping-specific notes: Detected outbound/inbound loss responses are printed as ">" and
           "<", respectively.  Receive errors are printed as "E".  Due to the asynchronous nature
           of 2ping, successful responses (backspaces) may overwrite these loss and error

       -i interval
           Wait interval seconds between sending each ping.  The default is to wait for one
           second between each ping normally, or not to wait in flood mode.  Only super-user may
           set interval to values less 0.2 seconds.

       -I interface IP
           Set source IP address.  When pinging IPv6 link-local address this option is required.
           When in listener mode, this option may be specified multiple to bind to multiple IP
           addresses.  When in client mode, this option may only be specified once, and all
           outbound pings will be bound to this source IP.

           2ping-specific notes: This option only takes an IP address, not a device name.  Note
           that in listener mode, if the machine has an interface with multiple IP addresses and
           an request comes in via a sub IP, the reply still leaves via the interface's main IP.
           So this option must be used if you would like to respond via an interface's sub-IP.

       -l preload
           If preload is specified, 2ping sends that many packets not waiting for reply.  Only
           the super-user may select preload more than 3.

       -p pattern
           You may specify up to 16 "pad" bytes to fill out the packets you send.  This is useful
           for diagnosing data-dependent problems in a network.  For example, -p ff will cause
           the sent packet pad area to be filled with all ones.

           2ping-specific notes: This pads the portion of the packet that does not contain the
           active payload data.  If the active payload data is larger than the minimum packet
           size (--min-packet-size=min), no padding will be sent.

       -q  Quiet output.  Nothing is displayed except the summary lines at startup time and when

       -s packetsize
           ping compatibility, this will set --min-packet-size to this plus 8 bytes.

       -v  Verbose output.  In 2ping, this prints decodes of packets that are sent and received.

       -V  Show version and exit.

       -w deadline
           Specify a timeout, in seconds, before 2ping exits regardless of how many pings have
           been sent or received.  Due to blocking, this may occur up to one second after the
           deadline specified.

           2ping-specific notes: This option behaves slightly differently from ping.  If both -c
           and -w are specified, satisfaction of -c will cause an exit first.

       2ping-specific options:

       -?, --help
           Print a synposis and exit.

       -6, --ipv6
           Bind/connect as IPv6.

           Set a shared key, send cryptographic hashes with each packet, and require
           cryptographic hashes from peer packets signed with the same shared key.

           When --auth is used, specify the digest type to compute the cryptographic hash.  Valid
           options are hmac-md5 (default), hmac-sha1 and hmac-sha256.  hmac-md5 requires
           Digest::MD5, and the SHA digests require Digest::SHA.

           Print (lots of) debugging information.

           Wait at least secs seconds before inquiring about a lost packet.  Default is 10
           seconds.  UDP packets can arrive delayed or out of order, so it is best to give it
           some time before inquiring about a lost packet.

           Start as a listener.  The listener will not send out ping requests at regular
           intervals, and will instead wait for the far end to initiate ping requests.  A
           listener is required as the remote end for a client.

           Set the minimum total payload size to min bytes, default 64.  If the payload is
           smaller than min bytes, padding will be added to the end of the packet.

           Set the maximum total payload size to max bytes, default 512, absolute minimum 64.  If
           the payload is larger than max bytes, information will be rearranged and sent in
           future packets when possible.

           Do not perform 3-way pings.  Used most often when combined with --listen, as the
           listener is usually the one to determine whether a ping reply should become a 3-way

           Strictly speaking, a 3-way ping is not necessary for determining directional packet
           loss between the client and the listener.  However, the extra leg of the 3-way ping
           allows for extra chances to determine packet loss more efficiently.  Also, with 3-way
           ping disabled, the listener will receive no client performance indicators, nor will
           the listener be able to determine directional packet loss that it detects.

           Simulate random packet loss outbound and inbound.  For example, 25:10 means a 25%
           chance of not sending a packet, and a 10% chance of ignoring a received packet.  A
           single number without colon separation means use the same percentage for both outbound
           and inbound.

           Use UDP port port.  With --listen, this is the port to bind as, otherwise this is the
           port to send to.  Default is UDP port 15998.

           Print a line of brief current statistics every interval seconds.  The same line can be
           printed on demand by sending SIGQUIT to the 2ping process.


       There are probably lots and lots and lots of unknown bugs.

       By default, source IP logic doesn't work as expected, see -I for details.  There appears
       to be no way to peg the source IP of reply UDP packets to the destination of the packet
       that is being replied to.  As a result, packets always go out the interface's main IP
       address if not specified manually.  (Please, prove the author wrong.)

       This manpage isn't finished yet, and may never be.


       2ping was written by Ryan Finnie <>.

                                            2012-01-01                                   2PING(8)