Uplog is an UDP-based ping program that gives an ASCII
graphical log of packet loss. Once per second, it sends a UDP
packet to the echo port of the target host and waits for a
reply. If it gets a reply an X is written, otherwise a dot is
written to the log file. If a packet with an incorrect sequence
number arrives, a colon is written to the log file. By
examining the log file, one can easily see when and how the
packet losses occur.

WWW: http://www.nerdlabs.org/projects/uplog.php