在准备好从中读取的多个套接字中进行选择 [英] selecting among multiple sockets that are ready to be read from

问题描述

我正在编写一个服务器-客户端应用程序.我有一个服务器，其中包含我从 ServerSocket 的 accept() 方法获得的多个套接字.我想从这些套接字中读取数据，但我不一定知道哪个套接字已准备好可供读取.我需要某种选择器来选择一个准备好从中读取的套接字，以便我可以读取它发送的数据.

I am writing a server-client application. I have a server that holds several sockets that I have got from the accept() method of ServerSocket. I want to read from these sockets but I don't necesserally know which socket is ready to be read from. I need some kind of selector that will select one of the sockets that are ready to be read from, so I can read the data it sends.

谢谢.

推荐答案

基本上有两个选项可以使它工作:

You have basically two options to make it work:

1. 每个接受的套接字都有专用线程.这是因为常规"套接字 I/O 正在阻塞.您不能使用单个线程有选择地处理多个套接字.由于没有窥视"功能，当您调用 read 时，您将始终面临被阻止的风险.通过为您感兴趣的每个套接字设置一个线程，阻塞读取不会阻塞任何其他操作(线程).
2. 使用蔚来.NIO 允许异步 I/O 操作，基本上正是您所要求的 - Selector.

1. Have dedicated thread per accepted socket. This is because the 'regular' socket I/O is blocking. You can not selectively handle multiple sockets using a single thread. And as there is no 'peeking' functionality, you will always take a risk of getting blocked when you invoke read. By having a thread per each socket you are interested in reading, blocking reads will not block any other operations (threads).
2. Use NIO. NIO allows for asynchronous I/O operations, and basically exactly what you asked for - a Selector.

如果您决定采用 NIO 方式，我建议您查看 MINA 和 Netty.我发现它们比普通的 NIO 更容易使用.您不仅会获得更好的 API 来使用，而且至少 MINA 也有解决一些讨厌的 NIO 错误的方法.

If you do decide to go NIO-way, I would recommend checking out MINA and Netty. I've found them much easier to work with than plain NIO. Not only will you get a nicer API to work with, but at least MINA had workarounds for some nasty NIO bugs, too.

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