小编Imm*_*ity的帖子

我使用的是Netty 3.2.7.我正在尝试在我的客户端编写功能,这样如果在一定时间(例如30秒)之后没有写入消息,则会向服务器发送"保持活动"消息.

经过一番挖掘,我发现WriteTimeoutHandler应该让我这样做.我在这里找到了这个解释:https://issues.jboss.org/browse/NETTY-79.

Netty文档中给出的示例是:

public ChannelPipeline getPipeline() {
     // An example configuration that implements 30-second write timeout:
     return Channels.pipeline(
         new WriteTimeoutHandler(timer, 30), // timer must be shared.
         new MyHandler());
 }

在我的测试客户端,我做到了这一点.在MyHandler中,我还覆盖了exceptionCaught()方法:

public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
    if (e.getCause() instanceof WriteTimeoutException) {
        log.info("Client sending keep alive!");
        ChannelBuffer keepAlive = ChannelBuffers.buffer(KEEP_ALIVE_MSG_STR.length());
        keepAlive.writeBytes(KEEP_ALIVE_MSG_STR.getBytes());
        Channels.write(ctx, Channels.future(e.getChannel()), keepAlive);
    }
}

无论客户端在什么时间内没有向通道写入任何内容,我从未调用过覆盖的exceptionCaught()方法.

查看WriteTimeoutHandler的源代码,其writeRequested()实现是:

public void writeRequested(ChannelHandlerContext ctx, MessageEvent e)
        throws Exception {

    long timeoutMillis = getTimeoutMillis(e);
    if (timeoutMillis > 0) …