Java Sockets and Dropped Connections

Question

What\'s the most appropriate way to detect if a socket has been dropped or not? Or whether a packet did actually get sent?

I have a library for sending Apple Push N

Answer 1

This not be of much help to you, but technically both of your proposed solutions are incorrect. OutputStream.flush() and whatever else API calls you can think of are not going to do what you need.

The only portable and reliable way to determine if a packet has been received by the peer is to wait for a confirmation from the peer. This confirmation can either be an actual response, or a graceful socket shutdown. End of story - there really is no other way, and this not Java specific - it is fundamental network programming.

If this is not a persistent connection - that is, if you just send something and then close the connection - the way you do it is you catch all IOExceptions (any of them indicate an error) and you perform a graceful socket shutdown:

1. socket.shutdownOutput();
2. wait for inputStream.read() to return -1, indicating the peer has also shutdown its socket