Configure a Java Socket to fail-fast on disconnect?

Question

Hi,

I have a listening port on my server that I'm connecting to using a Java class and the Socket interface, i.e.

Socket mySocket = new Socket(host,port);

I then grab an OutputStream, decorate with a PrintWriter in autoflush mode and I'm laughing - except if the listening port closes. Then I get

tcp4       0      0  *.9999                 *.*                    LISTEN
tcp        0      0  127.0.0.1.45737        127.0.0.1.9999         CLOSE_WAIT

and I can't seem to detect the problem in the program - I've tried using the isConnected() Socket method but it doesn't seem to know that the connection is closed.

I want to be aware of the problem the next time I try and write to the Socket so that I can try and reconnect and report the issue.

Any advice please?

Thanks all

Answer 1

Set a short timeout?

Does isOutputShutdown() not get you what you want?

You could always build a SocketWatcher class that spins up in its own Thread and repeatedly tries to write empty strings to the Socket until that raises a SocketClosedException.

Answer 2

Hoped there'd be a more elegant way.. oh well

Answer 3

Set a different thread to reading from the socket. It will block until the socket is closed, and then an exception will be thrown. Catch that exception to detect the close immediately.