tcp_server is a simple, easily configurable tcp server for serving up multiple 'servlet' like processes. The servlet's can be extremely simple: No socket handling is required for the servlet, all it needs to do is read from stdin, and write to stdout. See the README for more information.
Tcpblocker is for sites that want to limit the number of times an IP address can connect to a tcpserver controlled service like SMTP within a time period. Each time tcpblock runs, it counts how many connections were made per client IP. If an IP exceeds the configurable maximum number of connections within the configurable time period, then tcpblock outputs a standard deny line that can be used to build a tcp.smtp style file. Combined with a cron job and a run script, tcpblocker can be configured to fit into just about any qmail or tcpserver installation.
Tcpbroker does TCP port forwarding with a twist: it connects two incoming sockets together. Tcpbroker allows you to telnet out from behind a firewall to another system also behind a firewall via a proxy host running the broker. All you need to do is remote command the far system to make the outgoing connection to the broker. Tcpbroker includes a secure authentication mechanism via Tiny SRP. A version without authentication is also included.
TcpCat is a very lightweight TCP utility. It takes an IP address and a TCP port as argument, connects to it, and gives the result back to stdout. It was written as a lightweight version of netcat. As such, it works like the Unix cat command, but instead of displaying a file it displays the result from a TCP service.
tcpflow is a program that captures data transmitted as part of TCP connections (flows), and stores the data in a way that is convenient for protocol analysis or debugging. tcpflow understands TCP sequence numbers and will correctly reconstruct data streams regardless of retransmissions or out-of-order delivery. Each stream is stored in a separate file for later analysis. tcpflow is designed to be portable, using the LBL packet capture library and GNU autoconf. It works under most UNIX platforms and for most common network interface types (ethernet, PPP, loopback, etc.).
tcpick is a textmode sniffer that can track TCP streams and saves the data captured in files or displays them in the terminal. It is useful for picking files in a passive way. It can store all connections in different files, or it can display all the stream on the terminal (using colors too).
The tcpsound utility plays sounds in response to network traffic, making it possible for a user to literally listen to a network. It forks a pseudo terminal in which to run tcpdump, parses that output, and plays a wide variety of user-configurable sounds. By interpreting the output in a pseudo terminal, users can first SSH to a remote host if desired.