SendIP is a command-line tool to send arbitrary IP packets. It has a large number of options to specify the content of every header of a RIP, RIPng, BGP, TCP, UDP, ICMP, or raw IPv4/IPv6 packet. It also allows any data to be added to the packet. Checksums can be calculated automatically, but if you wish to send out wrong checksums, that is supported too.
Sizzle is a Scheme interpreter for embedding into C applications and for standalone scripting. It implements a nearly complete subset of R5RS Scheme, adding a lot of primitives for U*ix scripting, regular expression searching, a simple module system, dynamic library linking, powerful string processing procedures, and much more. It includes a user's guide and an embedding manual in texinfo format, some examples, the embedding library, and a standalone interpreter for interactive use and scripting.
pftp allows you to send and receive files and directories recursively, send and receive standard input and ouput, filter your connection, set the net buffer size, set the bandwidth, send UDP datagrams unicasted, broadcasted, and multicasted (which is meant for AUDIO and VIDEO streaming), send data to another user and manage that data, perform a network test based on either UDP or TCP, and use optimized buffers for your Gigabit Ethernet links. pftp can start from command line, as a daemon, or by inetd. All features are supported for IPv4 and IPv6.