After channel close, read and write calls were using recycled file descriptor about jnr-unixsocket

[headius]

Hmm... so either we or the native IO subsystem is reusing the file descriptor and when we close it we're not properly killing the channel. Seems like marking the channel as closed would work here, right?

[headius]

Looks like we are not mimicking the SocketChannelImpl logic for checking openness on read and write. They have a number of places where they ensureOpen() and reads and writes check whether input or output have been shut down by looking at a flag. UnixSocketChannel appears to have none of this.

Easy one for someone to contribute... just look at how SocketChannelImpl (in the JDK) handles these openness checks.