How to terminate a thread blocking on socket IO operation instantly?

Question

In the context of Java, I create a new thread to read network input when open a GUI window, and when i close the window, i want to release the socket resource and terminate the thread immediately. Now i am using setSoTimeout method, but i don't want to wait the timeout exception. Could anybody give some suggestion? Thanks!

Answer 1

There are (potentially) three ways to do this:

• Calling Socket.close() on the socket will close the associated InputStream and OutputStream objects, and cause any threads blocked in Socket or (associated) stream operations to be unblocked. According to the javadoc, operations on the socket itself will throw a SocketException.

• Calling Thread.interrupt() will (under some circumstances that are not specified) interrupt a blocking I/O operation, causing it to throw an InterruptedIOException.

  ^{Note the caveat. Apparently the "interrupt()" approach doesn't work on "most" modern Java platforms. (If someone else had the time and inclination, they could possible investigate the circumstances in which this approach works. However, the mere fact that the behavior is platform specific should be sufficient to say that you should only use it if you only need your application to work on a specific platform. At which point you can easily "try it" for yourself.)}

• A possible third way to do this is to call Socket.shutdownInput() and/or Socket.shutdownOutput(). The javadocs don't say explicitly what happens with read and/or write operations that are currently blocked, but it is not unreasonable to think that they will unblock and throw an exception. However, if the javadoc doesn't say what happens then the behavior should be assumed to be platform specific.