在ServerSocket和ServerSocketChannel中接受并绑定

Question

So I've been going through Sam's Teach Yourself Java in 21 day on the topic of "Communicating Across the Internet". Within this dense chapter, one thing it lacks is the relationship between ServerSocketChannel and ServerSocket . It's especially perplexing when I read this:

ServerSocketChannel sockChannel = ServerSocketChannel.open();
sockChannel.configureBlocking(false);   

InetSocketAddress server = new InetSocketAddress("localhost", 79);

ServerSocket socket = sockChannel.socket();
socket.bind(server);

...

That ServerSocket object is never used in the rest of the code.

Reading through Java's Documentation, I get that ServerSocketChannel is used for non-blocking purposes when listening for connections while ServerSocket does block.

1. So the question is why is the code creating a ServerSocketChannel object (non-blocking) when it's using that to create a ServerSocket object (blocking) to bind to the address?

2. What would have been the difference if I just used ServerSocketChannel 's bind() instead of ServerSocket 's?

The same question applies for the accept() method as well for both classes.

Answer 1

So the question is why is the code creating a ServerSocketChannel object (non-blocking) when it's using that to create a ServerSocket object (blocking) to bind to the address?

I thing your tutorial was written before Java 1.7 was released. The ServerSocketChannel.bind() was added in java 1.7 release. Before that you needed to get the socket to bind the address.

What would have been the difference if I just used ServerSocketChannel's bind() instead of ServerSocket's?

Should be no difference.

The same question applies for the accept() method as well for both classes.

Here there is a difference: ServerSocket.accept() always blocks, while ServerSocketChannel.accept() can be configured to not block as you did in the example with sockChannel.configureBlocking(false);