Android:Socket output is shutdown

 SocketChannel socketChannel;
 ByteBuffer sendBuffer;
 //省略连接部分代码....但确保socketChannel已经和服务器socket连接上了
 sendBuffer = ByteBuffer.wrap("hello".getBytes("UTF8"));
 socketChannel.write(sendBuffer);

最后一行抛出异常java.net.SocketException: Socket output is shutdown