- have finish c.s. return the #bytes sent
- implement sendport sent-bytes call
- let the other drivers with a subOutput implement the flushBuffers()
  call in the same way as NetSerializationOutput
- investigate any deadlocks with NetGM rendez-vous (see SOR/IPL with
  async sends)
- investigate other NetGM deadlocks resulting from lack of flow-control when
  several nodes are sending to a single node.
