Gnutella crawler aren't open source because they can harm the network a lot. You can always ask the Gnutella developer forum http://groups.yahoo.com/group/the_gdf/ but I doubt they'll give you code. I warn you, crawling can be VERY damaging and should be done the LEAST times as possible.

Ciao

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Liens d'intérêt /Links of interest:
Gnutellaforums en français /The House's rules you have to respect / First search the forum, then create a thread / Free software alternatives! - Logiciels alternatifs gratuits!/