I/O Ninja is a tool for developers and hobbyists working in the field of computer communications. It artfully combines several facilities usually found in separate tools, such as a network sniffer and a terminal application.

Besides traditional network sniffer, serial and TCP connections, Ninja supports a set of unique modes. For example, Ninja is capable of accepting connections, handling named pipes or connectionless UDP (including UDP broadcasts and working with multiple UDP nodes simultaneously).

Another unique Ninja feature is the socket proxy: working as a transparent link in a connection, Ninja captures communications between two peers, thus allowing data monitoring in circumstances where a regular sniffer cannot be used, or requires additional hardware (e.g, for monitoring WiFi communications).

Additionally, the new version of Ninja now includes a feature only to be found in much more expensive software: A serial monitor. This monitor is capable of capturing all ongoing serial (COM, Bluetooth) communications sessions on the local computer, or even on a remote computer.

I/O Ninja's patent-pending log engine can represent data either in HEX or plain-text form. Log contents is context-colored, and includes status messages interwoven into the traffic logged, as they occur.

Data to be transmitted may be prepared in form of a HEX or plain-text packet. It may also be sent in real-time as the user types (terminal emulation).