SctpTransport.start(): invalid remotePort argument

[aboba]

When SctpTransport.start() is called with a remotePort argument, it is possible for the remotePort to be invalid. For example, since the SctpTransport uses Simultaneous Open (SO), this implies that both the local and remote ports need to be unique. The SctpTransport constructor will throw an exception if the local port isn't unique, but the remotePort exchanged in signaling might not be unique. Therefore the start() text should indicate that an InvalidParameters exception is thrown if the supplied remotePort (or the default value, port) isn't unique.