Java nio 连接正在创建多个套接字级别的连接，为什么? [英] Java nio connection is creating multiple socket level connections, Why?

问题描述

我写了一个简单的java nio程序，如下所示

I have written a simple java nio program like the below

 public static void main(String[] args) throws IOException, InterruptedException {


    InetSocketAddress address = new InetSocketAddress("127.0.0.1",1001);
    Selector incomingMessageSelector = Selector.open();
    SocketChannel socketChannel = SocketChannel.open();
    socketChannel.configureBlocking(false);   

//到这里代码创建了到端口 52209 和 52210 的前 2 个连接

// Till here the code creates the top 2 connections to port 52209 and 52210

    socketChannel.connect(address);
    socketChannel.register(incomingMessageSelector, SelectionKey.OP_CONNECT);
    socketChannel.register(incomingMessageSelector, SelectionKey.OP_WRITE);
    socketChannel.register(incomingMessageSelector, SelectionKey.OP_READ);

//然后它会创建 2 个到端口 1001 的连接

// Then it creates 2 connections to port 1001

    Thread.sleep(900000L);
}

我想了解为什么它会创建 4 个连接，而使用标准 TCP 阻塞库，它往往会创建 2 个连接.

I want to understand why it creates 4 connections, with the standard TCP blocking library it tends to create 2 connections.

我使用 JDK 1.7 和 Windows 7.

I use JDK 1.7 and Windows 7.

在图像中，只有 4 个突出显示的连接是由客户端创建的.

In the image only the 4 highlighted connections are of interest which are created by the client.

用红色标记的连接 1 条目是服务器端口.

One connection 1 entry marked with red is the server port.

PFA 显示这 4 个连接的图像.

PFA a image which shows these 4 connections.!

嗯，我真的最不明白为什么

Well i acutally most puzzled about why

Selector incomingMessageSelector = Selector.open();

在动态端口上创建连接

推荐答案

1001 和 52211 之间的连接显示两次，每个方向一次，因为两个端口都是本地端口.

The connection between 1001 and 52211 is being shown twice, once in each direction, as both ports are local.

一个选择器可能会打开另一个侦听套接字，以防它必须处理子选择器，以免超过每个选择器的最大套接字数.

A Selector may open another listening socket in case it has to handle sub-selectors so as not to exceed the maximum number of sockets per selector.

在完成 OP_CONNECT pgphasr 之前，您不应注册 OP_READ 或 OP_WRITE，此时您还应该注销 OP_CONNECT.同时注册这三个人绝对是错误的.

You shouldn't register OP_READ or OP_WRITE until after you've finished the OP_CONNECT pgphasr, when you should also deregister OP_CONNECT. Having all three of those registered at the same time is definitely wrong.

这篇关于Java nio 连接正在创建多个套接字级别的连接，为什么?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！