@RayManiac The error text shows 10061, different from the title... Looking up 10061 turns up a probable cause: "TCP error code 10061: No connection could be made because the target machine actively refused it."
My first suggestion would be to try UDP mode instead of TCP. I'm not a networking expert, but if I'm not mistaken, TCP requires the target machine to have opened the port already and be prepared for the initial handshaking. If it isn't ready, then the connection can't be established.
UDP doesn't do any handshaking, so it may succeed where TCP failed.
UDP should be ok on a LAN.
[netsend -u port]
Also add a -b flag if you're sending OSC packets.
Also it's highly recommended to use high port numbers for private connections. Lower port numbers may already be in use by the system -- a port number collision would cause the object to fail. Try in the 30000s or 40000s, or at least above 7000.