A all-in-one network diagnostics tool for BeOS legacy/classic network_server and bone network stack.
ping / traceroute / whois / dns / finger / port scann / DoS simulation / etc ... all wrapped in a nice UI.
PortSpy was widely used amoung the BeOS users, and have continuous featuer requrests and development over its lifetime.
More notable however, is internal to Be Inc. PortSpy was used as one of the goto tools to validate transition to BONE. And was, in general quite poplular within engeneering.
Its traceroute/ping cababilites exposed otherwise undocumented / under-document features of the networking stack and provided unique development opertunities.
WebSpeed (a late addition in its life) became quite populare for DevOps