Problem about Non-blocking socket's read and write

Question

my aim is:when I open a socketchannel,I can use this socket which can continue send and get messages!(for example:open a socket,send a loging message,server echo,if passed,use the same socket sending other message,get echo messages....
Here is problem sample codes:
void ConnectServer() throws IOException
bf = ByteBuffer.allocateDirect(1024);
InetSocketAddress ad = new InetSocketAddress(this.servername,this.serverport);
this.clientsocketchannel = SocketChannel.open(); //set socketchannel
this.clientsocketchannel.configureBlocking(false);
this.clientsocketchannel.connect(ad);
this.slt = Selector.open();
this.clientsocketchannel.register (this.slt,SelectionKey.OP_CONNECT|SelectionKey.OP_READ|SelectionKey.OP_WRITE);
//send data
private void SendMessage(byte[] SendMessage)throws IOException
while (this.slt.select() > 0)//sth wrong!when I test,slt.select(500)=0
Set readykey = slt.selectedKeys();
Iterator readyitor = readykey.iterator();
while (readyitor.hasNext())
SelectionKey skey = (SelectionKey) readyitor.next();
readyitor.remove();
if (skey.isWritable())
SocketChannel keychannel = (SocketChannel) skey.channel();
keychannel.write(ByteBuffer.wrap(this.sendmessage));
}//end while
}//end while
//get data
private void GetEchoMessage()throws IOException
while(this.slt.select(500) > 0)//sth wrong!when I test,slt.select(500)=0
Set readykey = slt.selectedKeys();
Iterator readyitor = readykey.iterator();
while (readyitor.hasNext())
SelectionKey skey = (SelectionKey) readyitor.next();
readyitor.remove();
if (skey.isWritable())
SocketChannel keychannel = (SocketChannel) skey.channel();
keychannel.read(bf);
public static void main(String[] arg)
connectserver(..);
SendMessage(...);
GetEchoMessage();
SendMessage(...);
GetEchoMessage();

Answer 1

private void ConnectServer() throws IOException
� bf = ByteBuffer.allocateDirect(1024);
�� InetSocketAddress ad = new InetSocketAddress(this.servername,this.serverport);
�� this.clientsocketchannel = SocketChannel.open(); //set
socketchannel
�� this.clientsocketchannel.configureBlocking(false);
�� this.clientsocketchannel.connect(ad);
�� this.slt = Selector.open(); � this.clientsocketchannel.registerthis.slt,SelectionKey.OP_CONNECT|SelectionKey.OP_READ|SelectionKey.OP_WRITE);
<b>
//send data</b>
private void SendMessage(byte[] SendMessage)throws IOException
� while (this.slt.select() > 0)//<font color="#FF0000"><i>wrong,when test,this.slt.select(500)=0,why??</i></font>
�{
��� Set readykey = slt.selectedKeys();
��� Iterator readyitor = readykey.iterator();
��� while (readyitor.hasNext())
��� {
������ SelectionKey skey = (SelectionKey) readyitor.next();
������ readyitor.remove();
������ if (skey.isWritable())
������ {
�������� SocketChannel keychannel = (SocketChannel) skey.channel();
�������� keychannel.write(ByteBuffer.wrap(this.sendmessage));
������ }
��� }//end while
� }//end while�
<b>
//get data</b>
private void GetEchoMessage()throws IOException
� while(this.slt.select(500) > 0)<font color="#FF0000"><i>//wrong,when
test,this.slt.select(500)=0</i></font>
� {
��� Set readykey = slt.selectedKeys();
��� Iterator readyitor = readykey.iterator();
��� while (readyitor.hasNext())
��� {
����� SelectionKey skey = (SelectionKey) readyitor.next();
����� readyitor.remove();
����� if (skey.isWritable())
����� {
������� SocketChannel keychannel = (SocketChannel) skey.channel();
������� keychannel.read(bf);
����� }
��� }
� }
public static void main(String[] arg)
� ......
� connectserver(..);
� SendMessage(...);
� GetEchoMessage();
� .......
� SendMessage(...);
� GetEchoMessage();
� .......