NetCrypt!

Netcat is a featured networking utility which reads and writes data across network connections, using the TCP/IP protocol. It is designed to be a reliable "back-end" tool that can be used directly or easily driven by other programs and scripts. At the same time, it is a feature-rich network debugging and exploration tool, since it can create almost any kind of connection you would need and has several interesting built-in capabilities.

Dropbear is a relatively small SSH 2 server and client. It runs on a variety of POSIX-based platforms. Features: A small memory footprint suitable for memory-constrained environments - Dropbear can compile to a 110kB statically linked binary with uClibc on x86 (only minimal options selected).Dropbear server implements X11 forwarding, and authentication-agent forwarding for OpenSSH clientsCan run from inetd or standalone.Compatible with OpenSSH ~/.ssh/authorized_keys public key authentication.The server, client, keygen, and key converter can be compiled into a single binary (à la busybox).Features can easily be disabled when compiling to save space.TCP forwarding support »

socat is a relay for bidirectional data transfer between two independent data channels. Each of these data channels may be a file, pipe, device (serial line etc. or a pseudo terminal), a socket (UNIX, IP4, IP6 - raw, UDP, TCP), an SSL socket, proxy CONNECT connection, a file descriptor (stdin etc.), the GNU line editor (readline), a program, or a combination of two of these. These modes include generation of "listening" sockets, named pipes, and pseudo terminals.