In a server based on AsynchronousServerSocketChannel and AsynchronousSocketChannel, how can I check whether a connection from a given IP address already exists? I want to send a specific message to connections that come from an IP address that is already connected (asking it to try again later; I’m dealing with very specific client-side LANs whose bandwidth will be poorly utilized if shared rather than forced to serialize by the server). However, I see no way to get a list of IP addresses to search for whether the same IP address already has a connection. Is there a more elegant/efficient way to do this other than inserting the IP addresses of each new connection to (and removing them upon closing from) something like a ConcurrentSkipListSet?
Moreover, I want to periodically gather a few network statistics from all open connections (how many chunks of a file have been uploaded, say). The only way I came up with to do this efficiently is send updates from the completion handlers (of a chunk-sending network write) to the info gathering thread using ConcurrentLinkedQueue, waking the thread any time something is inserted into the queue. I’m assuming the wake operation is non-blocking but I don’t know how expensive it may be, as I’m sure at the very least it involves an interlocked CPU instruction (which implies a memory fence and affects execution speed even further etc.). Any other suggestions?
You will have to maintain your own data structures. All TCP will give you is the sockets, from which you can get their remote addresses and ports.