'Create an instance of the server side of the SSH protocol.
@type addr: L{twisted.internet.interfaces.IAddress} provider
@param addr: The address at which the server will listen.
@rtype: L{twisted.conch.ssh.transport.SSHServerTransport}
@return: The built transport.'

def buildProtocol(self, addr):

    t = protocol.Factory.buildProtocol(self, addr)
    t.supportedPublicKeys = self.privateKeys.keys()
    if (not self.primes):
        log.msg('disabling    non-fixed-group    key    exchange    algorithms    because    we    cannot    find    moduli    file')
        t.supportedKeyExchanges = [kexAlgorithm for kexAlgorithm in t.supportedKeyExchanges if (_kex.isFixedGroup(kexAlgorithm) or _kex.isEllipticCurve(kexAlgorithm))]
    return t
