The JNLP v2 protocol has a sub par write implementation if there is more than one buffers worth of data to be written to the network.
The current implementation writes one buffers worth and then exits - waiting for another callback from the selector before writing another buffer.
The code should write as much data as possible before returning back.

see https://github.com/jenkinsci/remoting/blob/c3e675c9f1dc29a8fd99eca191c1ce1e5ebb2a7e/src/main/java/org/jenkinsci/remoting/protocol/impl/NIONetworkLayer.java#L191-L227