Java Sockets: check if client is able to receive message from server

Question

When I flush() the message from the server's OutputStream, the client either received message or not (if it was disconnected before timeout). I need to somehow control this situation from server-side, I have to know if client is able to receive the message before sending it. How it could be done?

Answer 1

In the past, I have typically used a blocking read in a separate thread to read client messages and disseminate them as needed.

If the client disconnects, the InputStream.read() operation returns -1 and we take that as notification that the client has "disconnected" and the InputStream should be closed. It may also throw an IOException if the connection is abnormally terminated.

You can then test Socket.isClosed() to verify whether or not you can still write messages.