Netty启动步骤绑定端口示例方法源码分析

private ChannelFuture doBind(final SocketAddress localAddress) {
    //初始化并注册(1)
    final ChannelFuture regFuture = initAndRegister();
    //获得channel(2)
    final Channel channel = regFuture.channel();
    if (regFuture.cause() != null) {
        return regFuture;
    }
    if (regFuture.isDone()) {
        ChannelPromise promise = channel.newPromise();
        //绑定(3) 
        doBind0(regFuture, channel, localAddress, promise);
        return promise;
    } else {
        //去除非关键代码
        return promise;
    }
}

final Channel channel = regFuture.channel();

private static void doBind0(final ChannelFuture regFuture, final Channel channel, final SocketAddress localAddress, final ChannelPromise promise) { 
    channel.eventLoop().execute(new Runnable() {
        @Override
        public void run() {
            if (regFuture.isSuccess()) {
                //绑定端口
                channel.bind(localAddress, promise).addListener(ChannelFutureListener.CLOSE_ON_FAILURE);
            } else {
                promise.setFailure(regFuture.cause());
            }
        }
    });
}

public ChannelFuture bind(SocketAddress localAddress, ChannelPromise promise) {
    //通过pipeline绑定端口
    return pipeline.bind(localAddress, promise);
}

public final void bind(final SocketAddress localAddress, final ChannelPromise promise) {
    //代码省略
    //端口绑定之前不是active, 返回false
    boolean wasActive = isActive();
    try {
        //做jdk底层的绑定
        doBind(localAddress);
    } catch (Throwable t) {
        //省略
        return;
    }
    //端口绑定之前不是active, 端口绑定之后变成active了
    if (!wasActive && isActive()) {
        invokeLater(new Runnable() {
            @Override
            public void run() {
                pipeline.fireChannelActive();
            }
        });
    }
    safeSetSuccess(promise);
}

protected void doBind(SocketAddress localAddress) throws Exception {
    //jdk版本的判断
    if (PlatformDependent.javaVersion() >= 7) {
        javaChannel().bind(localAddress, config.getBacklog());
    } else {
        javaChannel().socket().bind(localAddress, config.getBacklog());
    }
}

javaChannel().bind(localAddress, config.getBacklog());

public final void beginRead() {
    assertEventLoop();
    if (!isActive()) {
        return;
    }
    try {
        doBeginRead();
    } catch (final Exception e) {
        //代码省略
    }
}

protected void doBeginRead() throws Exception {
    //拿到selectionKey
    final SelectionKey selectionKey = this.selectionKey;
    if (!selectionKey.isValid()) {
        return;
    }
    readPending = true;
    //获得感兴趣的事件
    final int interestOps = selectionKey.interestOps();
    //判断是不是对任何事件都不监听
    if ((interestOps & readInterestOp) == 0) {
        //此条件成立
        //将之前的accept事件注册, readInterest代表可以读取一个新连接的意思
        selectionKey.interestOps(interestOps | readInterestOp);
    }
}