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javanio

Difference between socketChannel.register() and key.interestOps()?

What's the deference between SocketChannel.register() and SelectionKey.interestOps()?

In the echo NIO server found in this SO question, for every key that is accepted, a register is called for a read op. Then once a message is read, the register is called again for a write op. However, after writing a message, rather than registering another read op it calls key.interestOps(SelectionKey.OP_READ).

Why the difference?

Solution

  • register() will lose or change the key attachment, and possibly return a new SelectionKey altogether: it isn't specified. Use interestOps() in this situation.