NetworkingOptions are applied in AbstractIoHandler.sessioncCeated, which is called after the socket has been connected.

Although most socket options can be changed after the socket is connected, window scaling is negotiated during the initial handshake. Therefore the receive buffer size cannot be changed to more than 64k after the socket is connected.

Aside: Mina actually handles the receive buffer size as a special case in its own logic in order to work around this.