服务器不接受nio中的一个客户端

Question

Am trying to build a chat application.i have a code that sends the data from client to server. when one or more client login(when the client program runs one or more time).server will not accepting the rest of connection other than first connected. please help me to resolve this here is my code:

public class Server
{

//Creating non blocking socket

public void non_Socket() throws Exception {

    ServerSocketChannel ssChannel = ServerSocketChannel.open();
    int port = 80;
    int i=0;
    ssChannel.socket().bind(new InetSocketAddress(port));
    ssChannel.configureBlocking(false);
    while(true)
    {
        SocketChannel sc = ssChannel.accept();`

        if (sc == null) 
        {
            System.out.println("Socket channel is null");
            Thread.sleep(5000);
        }
        else 
        {
            System.out.println("Socket channel is not null");
            System.out.println("Received an incoming connection from " +
                    sc.socket().getRemoteSocketAddress()); 
            new PrintRequest(sc,i).start(); 
            i++;
        }
    }
}

public static void main(String [] abc) throws Exception
{
    new Server().non_Socket();
}
}

class PrintRequest extends Thread {

public  PrintRequest(SocketChannel sc,int i) throws Exception
{
    WritableByteChannel wbc = Channels.newChannel(System.out); 
    ByteBuffer b = ByteBuffer.allocateDirect(1024); // read 1024 bytes 
    int numBytesRead = sc.read(b);

    while (numBytesRead != -1) 
    {
        b.flip();

        while (b.hasRemaining())
        { 
            wbc.write(b);
            System.out.println();
            //System.out.println("Stream  "+i);
            // System.out.println("  KKK   "+b.toString());
        }
        //b.clear();
    }    
}
}

Client code:

public class Client extends Thread {

public void non_Client_Socket() throws Exception
{
    SocketChannel sChannel = SocketChannel.open();
    sChannel.configureBlocking(false);
    sChannel.connect(new InetSocketAddress("localhost", 80));
    while (!sChannel.finishConnect())
    {
        System.out.println("Channel is not connected yet");
    }

    System.out.println("Channel is ready to use");

    /* ----------  going to send data to server ------------*/   
    System.out.println("please enter the text");
    BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));
    while(true)
    {
        System.out.println("Enter the text");
        String HELLO_REQUEST =stdin.readLine().toString();
        if(HELLO_REQUEST.equalsIgnoreCase("end"))
        {
            break;
        }

        System.out.println("Sending a request to HelloServer");    
        ByteBuffer buffer = ByteBuffer.wrap(HELLO_REQUEST.getBytes());    
        sChannel.write(buffer); 
     }
}
     /* ----------  the data is written to sChannel server
                      will read from this channel  ------------   */

public static void main(String [] args) throws Exception
{
    new Client().non_Client_Socket();
}
}

Answer 1

There are numerous issues here.

1. You are putting your ServerSocketChannel into non-blocking mode and then calling accept() without using a Selector. That means 99.9999% of the time accept() will return null, so you are burning CPU cycles. This is pointless. Either accept in blocking mode or use a Selector.

2. You are putting your client SocketChannel into non-blocking mode, calling connect(), and the calling finishConnect() without using a Selector. That means 99% of the time finishConnect() will return false, so you are burning CPU cycles. This is pointless. Either connect in blocking mode or use a Selector.

3. You are ignoring the result of SocketChannel.write() . You can't do that. It returns information you need to know about.

In short, your code doesn't make much sense.

Answer 2

I don't have time to look into your code in detail, but some initial observations:

1. When using NIO, I suggest you use Selector (as I suggested in your previous question ) instead of one thread per client.

2. Remember to bind each client in order to allow the server socket to accept new connections.