Some general Java NIO questions

Networking & Multiplayer
#1

Hello,
today I have started with Java NIO, but it seems to be quite complex, hence I have some questions to which I couldn’t find any answer in those NIO tutorials I have read.

For learning purposes I want to implement some very common use cases:

  1. Sending serialized objects to a server, deserializing and storing them in a collection.
  2. Requesting data from a server. The data could be anything, maybe some objects in an array.

I don’t understand how ObjectInputStream/ObjectOutputStream and ByteBuffer work together and I’m not sure how many channels I need on the client and on the server. Do I need one socket channel on each side for each use case (4 socket channels altogether) or would one read-write-socket channel on each side be sufficient?

Thanks for all answers.

#2

Why did you decide to use NIO? It’s not a natural progression from old IO. You’re better off without it, even if you merely want to learn it for the sake of it - just don’t. At least, not until you have a solid understanding of old IO, and a specific need for new IO.

#3

Normal sockets need multiple threads to handle multiple clients concurrently, which would result in a cumbersome and resource-hungry multithreading implementation.

#4

Unless you actually have thousands of concurrent connections, it’s premature optimization.

#5

My goal is to get just a basic practical understanding of how this works, because it doesn’t have a lot in common with standard Java sockets. It just aroused my interest, the practical usage is another question.

#6

Given the questions in your first post (how to connect Streams to Channels, and whether to use 1 or 2 sockets per client), I’m fairly sure you simply need to study old IO and get real world experience with it (not just a simple request/reply server), before even considering NIO. Once you have experience with old IO, you’ll see that NIO is not that different and all NIO tutorials will make sense.

#7

That was a typo and I already changed that. I did not mean sockets, but socket channels.

#8

Same thing really. A NIO channel is an InputStream and OutputStream wrapped into one.

#9

With the new concurrent libraries and executor services threading is a piece of cake. You can now write a standard IO socket based server with threading that is dead simple compared to the old thread way or even with NIO.