searches n + ... + 3 + 2 + 1 times

You loop through your queue here:
https://github.com/indutny/node-nat-upnp/blob/master/lib/nat-upnp/ssdp.js#L109

And then you loop through the sockets inside of that loop before popping one off, here:
https://github.com/indutny/node-nat-upnp/blob/master/lib/nat-upnp/ssdp.js#L69

It looks like a bug, but it doesn't seem to break anything. Haven't dug deep enough to pull request, just making a note.

Start by reading the queue loop in lib/nat-upnp/ssdp.js around line 109 and the nested socket loop around line 69. Trace how sockets are removed and determine whether the repeated searches are unintended; done means the search behavior is correct without redundant iteration, with verification that NAT discovery still works.

Written by the indexing model from the issue text.