Tomcat的Socket实现：org.apache.tomcat.util.net（一）
org.apache.tomcat.util.net包的内容都与网络连接和socket有关，比较主要和常见的是JIOEndpoint这个类，前面提到Coyote连接器的时候，就有涉及到JIOEndpoint，它用于监听某个socket端口、将socket对象交给coyote，并提供基本的线程池功能。除了JIOEndpoint，还有AprEndpoint、NioEndpoint等。由于对apr和nio不熟悉，所以只研究了一下JIOEndpoint

org.apache.tomcat.util.net.JIoEndpoint
JIOEndpoint其实和我们本科时上计算机网络或者分布式系统，做实验写的socket服务器差不多，结构也是经典的“Listen-Accept-Handle”，这里简单描述一下：JIOEndpoint使用JDK的ServerSocket类监听某个端口，有socket连接进来的时候便返回一个socket对象，交给专门的处理器。当然，具体的实现没那么简单，下面会按照socket的处理过程，详细说明其中的机理。

初始化
public void init()
        throws Exception {

        if (initialized)
            return;
        // Initialize thread count defaults for acceptor
        if (acceptorThreadCount == 0) {
            acceptorThreadCount = 1;
        }
        if (serverSocketFactory == null) {
            serverSocketFactory = ServerSocketFactory.getDefault();
        }
        if (serverSocket == null) {
            try {
                if (address == null) {
                    serverSocket = serverSocketFactory.createSocket(port, backlog);
                } else {
                    serverSocket = serverSocketFactory.createSocket(port, backlog, address);
                }
            } catch (BindException be) {
                throw new BindException(be.getMessage() + ":" + port);
            }
        }
        //if( serverTimeout >= 0 )
        //    serverSocket.setSoTimeout( serverTimeout );
        initialized = true;
    }

在这里，利用serverSocketFactory新建了一个serverSocket对象，用于监听特定的端口

启动JIOEndpoint
// Create worker collection
            if (executor == null) {
                workers = new WorkerStack(maxThreads);
            }

            // Start acceptor threads
            for (int i = 0; i < acceptorThreadCount; i++) {
                Thread acceptorThread = new Thread(new Acceptor(), getName() + "-Acceptor-" + i);
                acceptorThread.setPriority(threadPriority);