PortPeeker is a standalone port listener, which uses whatever TCP/UDP port you specify and logs all incoming requests in detail. It provides a simple searchable text log overview of all connections that have taken place, as well as their details. In addition, a handy drop-down box on top lists all the IP addresses that have connected, and selecting on will let you jump to the associate log entries. PortPeeker can even send a user defined response to connection requests or data in events. Useful for application testing (errors can be logged as well) and security monitoring for vulnerable ports.
