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.