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
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
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.
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.
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 characters.
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.
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.
If preload is specified, 2ping sends that many packets not waiting for reply. Only the super-user may select preload more than 3.
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.
Quiet output. Nothing is displayed except the summary lines at startup time and when finished.
ping compatibility, this will set --min-packet-size to this plus 8 bytes.
Verbose output. In 2ping, this prints decodes of packets that are sent and received.
Show version and exit.
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.
Print a synposis and exit.
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 ping.
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 58277 (WILLCHANGEINTHEFUTURE).
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.