Strange set of TCP ports

[Raistlin <raistlin () gioco net>]

Greetings,

can someone help me in identifying the following strange subset of open 
TCP ports ?
3687/tcp open  unknown
3688/tcp open  unknown
3689/tcp open  rendezvous
3690/tcp open  unknown
3691/tcp open  unknown

Googling or looking at the usual known ports lists do not yield any 
results. I'd like to identify this beast if possible. Thanks in advance.

Stefano


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