Hey
I only noticed that now. If you are unlucky enough to connect to a host that is configured to simply drop (as opposed to refuse) a connection on a non-existing or hidden port, Pd is blocked for as long as the requests reaches a time out. This can be very long, up to a few minutes and you can't do anything in the GUI (e.g. telling [tcpclient] to drop the connection) while it is waiting for the connection to establish.
Pd's [netsend] behaves the same, but this one I was expecting not to be threaded.
Roman