Background

These terminals demonstrate exactly how different protocols on the Internet work. It is important to understand the textual implications that all web-based applications have.

How do I use it?

TCP Hook
The TCP Hook is like a simple Telnet Utility. You can connect to a port and exchange data at the root level. The best way to understand what it does is to try it:
Type in a web site to the "Host" field and st the port to 80. Then hit connect and paste the following text in:

GET / HTTP/1.0

Then hit return twice. It should then display the HTTP headers and HTML of the chosen web site.

That is an example of how a web browser works. You can try it with any protocol (FTP, SMTP, POP3 etc).

TCP Listener

The TCP Listener does exactly as the Hook does, only it is for looking at the protocols sent by a protocol daemon. In other words, it is simulating a server. For example, you make a TCP listener listen on port 80, and then type "localhost" into your web browser, and you will see exactly what your web browser sends to every web site you visit.

UDP Terminal

Note: UDP Terminal is only available to users running OS 9, or OS X logged in as root. This is because Net Tool Box runs as a CFM Application in OS X, which means it must be properly authorized if using low level BSD commands.

UDP is the connectionless version of TCP. In other words, you can send and receive data packets, without having your terminal "bound" to a specific host, like with the TCP protocol. The UDP protocol is used on Local Area Networks for broadcasting and probing for computers on a network.

Although it is connectionless, the implementation in Net Tool Box requires you to bind to a host for sending data. You can still receive data from any host of you have the check box "Allow datagrams from other hosts" checked.

Problems

TCP listener can only listen on ports greater than 1024 when running on OS X as a non-root user. This is for the same reason that UDP Terminal only runs on OS X as root.