用户NIO写服务器，必须多加处理OP_WRITE，不会丢包

用户NIO写服务器，必须多加处理OP_WRITE，不会丢包

服务器往外发数据包，不是光一个socketChannel.write(bb); 就完事了


那是理想状态。。

用我方法才能保证发出，即使客户端连接很滥

public   static   long  flushChannel(SocketChannel socketChannel,ByteBuffer bb,  long  writeTimeout)  throws  IOException
  {

     SelectionKey key = null;
     Selector writeSelector = null;
     int attempts = 0;
     int bytesProduced = 0;
     try {
         while (bb.hasRemaining()) {
             int len = socketChannel.write(bb);
             attempts++;
             if (len < 0){
                 throw new EOFException();
             } 
             bytesProduced += len;
             if (len == 0) {
                 if (writeSelector == null){
                     writeSelector = Selector.open();
                     if (writeSelector == null){
                         // Continue using the main one
                         continue;
                     } 
                 }

                 key = socketChannel.register(writeSelector, key.OP_WRITE);

                 if (writeSelector.select(writeTimeout) == 0) {

                     if (attempts > 2)

                         throw new IOException("Client disconnected");

                 } else {

                     attempts--;

                 }

             } else {

                 attempts = 0;

             }

         }

     } finally {

         if (key != null) {

             key.cancel();

             key = null;

         }

         if (writeSelector != null) {

             // Cancel the key.

             writeSelector.selectNow();

             writeSelector.close();

         }

     }

     return bytesProduced;

 }