Some servents block out mp3 and some other words. Otherwise, everyone would search for mp3 and we'd have thousands of query hits flying back and forth, flooding the network. I suggest trying some other words, ones that give some responses when you search for them on your other gnutella servents. I get responses when I search for mp3, but I know I'm not getting the responses I would if newer servents weren't blocking queries like that.

Here is how I send queries -

0-15: GUID 16 numbers [same as ping GUID]
16: 0x80
17: ttl 7
18: hops 0
19: querylength+3
20-22: all 0's
23-24: all 0's
25 through querylength+25 : query
26+querylength: 0

I had trouble initially. I develop on Unix (Linux). What I did was install gnut, a working Gnutella servent and then tcpdump so I could see how it was sending queries properly. Then I ran tcpdump on my program and saw where I had gone wrong and fixed it.

There's a Windows version of tcpdump called windump, although I haven't used it. Tcpdump (and probably windump or some other packet sniffer) is quite handy in helping debug many Gnutella problems.