MasarLabs PatD is a daemon to ping or traceroute remote hosts, using IPv4 or IPv6 ICMP packets. It runs without root privileges, listening on a TCP local port for hosts to check. It uses a protocol simple to implement, so is useful in situations in which you cannot send native ICMP packets (for example, from a Java program). pat is a client you can use to talk to patd.
ip2clue provides access to multiple databases (Maxmind, Software 77, Webhosting.info and ip2location) to retrieve country information associated with IP addresses. It has a daemon that supports lots of concurrent connections and a client binary. Some client examples are also provided in languages including PHP and C.
conexus is a generalized C++ I/O library that includes network support for IPv4 and IPv6 sockets, serial/TTY communications, kernel message queues, pipes, and files. Objects use sigc++ for signaling property changes and other information. Sub-libraries include conexus-gtkmm (provides a set of gtkmm widgets), conexus-dbus (provides dbus support for endpoints), conexus-nspr (provides NSPR endpoints), conexus-nss (provides NSS endpoints), and conexus-ssl (provides OpenSSL endpoints).