【Netty源码分析】客户端connect服务端过程

上一篇博客【Netty源码分析】Netty服务端bind端口过程 我们介绍了服务端绑定端口的过程，这一篇博客我们介绍一下客户端连接服务端的过程。
ChannelFuture future = boostrap.connect("127.0.0.1", 8080).sync(); 调用BootStrap的connect函数public ChannelFuture connect(String inetHost, int inetPort) {
return connect(InetSocketAddress.createUnresolved(inetHost, inetPort));
}

public ChannelFuture connect(SocketAddress remoteAddress) {
if (remoteAddress == null) {
throw new NullPointerException("remoteAddress");
}

validate();
return doResolveAndConnect(remoteAddress, config.localAddress());
}

调用doResolveAndConnect函数 private ChannelFuture doResolveAndConnect(final SocketAddress remoteAddress, final SocketAddress localAddress) {
........
return doResolveAndConnect0(channel, remoteAddress, localAddress, channel.newPromise());
........
}

private ChannelFuture doResolveAndConnect0(final Channel channel, SocketAddress remoteAddress,
final SocketAddress localAddress, final ChannelPromise promise)
........

doConnect(remoteAddress, localAddress, promise);

........

}

调用doConnect函数时会同时开启一个线程，用来处理客户端的操作。
private static void doConnect(
final SocketAddress remoteAddress, final SocketAddress localAddress, final ChannelPromise connectPromise) {

// This method is invoked before channelRegistered() is triggered. Give user handlers a chance to set up
// the pipeline in its channelRegistered() implementation.
final Channel channel = connectPromise.channel();
channel.eventLoop().execute(new Runnable() {
@Override
public void run() {
if (localAddress == null) {
channel.connect(remoteAddress, connectPromise);
} else {
channel.connect(remoteAddress, localAddress, connectPromise);
}
connectPromise.addListener(ChannelFutureListener.CLOSE_ON_FAILURE);
}
});
}

AbstractChannel的connect函数
@Override
public ChannelFuture connect(SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise) {
return pipeline.connect(remoteAddress, localAddress, promise);
}

@Override
public final ChannelFuture connect(
SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise) {
return tail.connect(remoteAddress, localAddress, promise);
}

private void invokeConnect(SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise) {
if (invokeHandler()) {
try {
((ChannelOutboundHandler) handler()).connect(this, remoteAddress, localAddress, promise);
} catch (Throwable t) {
notifyOutboundHandlerException(t, promise);
}
} else {
connect(remoteAddress, localAddress, promise);
}
}HeadContext的connect函数@Override
public void connect(
ChannelHandlerContext ctx,
SocketAddress remoteAddress, SocketAddress localAddress,
ChannelPromise promise) throws Exception {
unsafe.connect(remoteAddress, localAddress, promise);
}AbstractUnsafe函数的connect函数@Override
public final void connect(
final SocketAddress remoteAddress, final SocketAddress localAddress, final ChannelPromise promise) {
.......

if (doConnect(remoteAddress, localAddress)) {
fulfillConnectPromise(promise, wasActive);
}

.......
}调用NioSocketChannle的doConnect函数 @Override
protected boolean doConnect(SocketAddress remoteAddress, SocketAddress localAddress) throws Exception {
if (localAddress != null) {
doBind0(localAddress);
}

boolean success = false;
try {
boolean connected = javaChannel().connect(remoteAddress);
if (!connected) {
selectionKey().interestOps(SelectionKey.OP_CONNECT);
}
success = true;
return connected;
} finally {
if (!success) {
doClose();
}
}
}或许执行doBind0函数
private void doBind0(SocketAddress localAddress) throws Exception {
if (PlatformDependent.javaVersion() >= 7) {
javaChannel().bind(localAddress);
} else {
javaChannel().socket().bind(localAddress);
}
}javaChannle()函数获得的就是SocketChannle对象，这样就完成了客户端连接服务端的操作。